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Chevrolet Lumina APV 1993 - 1993 ENGINE PERFORMANCE Self-Diagnostics - V6, Gas
Chevrolet Lumina APV 1993 - INTRODUCTION
Most engine control problems result from mechanical failures, poor electrical connections or damaged vacuum hoses. Before condemning the computer system, perform checks and inspections covered in BASIC TESTING article in this section. Failure to do so may result in lost diagnostic time.
If no faults were found while performing BASIC TESTING, proceed with DIAGNOSTIC PROCEDURE. If no fault codes or only a non-running Code 12 is present and driveability problems exist, proceed to TESTS W/O CODES article in this section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.). If only intermittent codes are present, see INTERMITTENTS in TESTS W/O CODES article in this section.
Chevrolet Lumina APV 1993 - TERMINOLOGY
Due to Federal government requirements, manufacturers may use names and acronyms for systems and components different than those used in previous years. The following table will help eliminate confusion when dealing with these components and systems. Only relevant components and systems whose names have changed from current General Motors Corp. terminology have been listed.
Chevrolet Lumina APV 1993 SAE TERMINOLOGY
Former Name Or Acronym New Name Or Acronym ALDL Data Link Connector (DLC) CHECK ENGINE Light Malfunction Indicator Light (MIL) CTS Engine Coolant Temperature Sensor Diagnostic Circuit Check On-Board Diagnostic (OBD) System Check ESC System Knock Sensor (KS) System EST System Ignition Control (IC) System MAT Sensor Intake Air Temperature (IAT) Sensor Park/Neutral (P/N) Switch Park/Neutral Position (PNP) Switch Port Fuel Injection Multi Port Fuel Injection Scan Data Scan Tester (ST) Data SERVICE ENGINE SOON Light Malfunction Indicator Light (MIL) Thermostatic Air Cleaner (TAC) Air Cleaner (ACL) Throttle Position Sensor (TPS) Throttle Position (TP) Sensor Throttle Position Switch Closed Throttle Position (CTP) Switch Throttle Position Switch Wide Open Throttle (WOT) Switch Viscous Converter Clutch (VCC) Torque Converter Clutch (TCC)
Chevrolet Lumina APV 1993 - SELF-DIAGNOSTIC SYSTEM
All vehicle are equipped with either an Electronic Control Module (ECM), Powertrain Control Module (PCM) or Vehicle Control Module (VCM). Unless specifically stated, references to ECM also apply to PCM or VCM equipped vehicles.
The ECM is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, ECM will illuminate the SERVICE ENGINE SOON light located on instrument panel. This light is also referred to as the Malfunction Indicator Light (MIL). When malfunction is detected and MIL is turned on, a corresponding trouble code will be stored in ECM memory. To retrieve stored codes, see READING TROUBLE CODES or RETRIEVING CODES (NON-SCAN). Malfunctions are recorded as HARD FAILURES or as INTERMITTENT FAILURES.
Chevrolet Lumina APV 1993 - HARD FAILURES
Hard failures cause MIL to illuminate and remain on until the malfunction is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause must be found using diagnostic (code) charts. If a sensor fails, control unit will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional, but driveability can be poor.
Chevrolet Lumina APV 1993 - INTERMITTENT FAILURES
Intermittent failures cause MIL to flicker or illuminate and go out about 10 seconds after the intermittent fault goes away. The corresponding trouble code, however, will be retained in ECM memory. If related fault does not reoccur within 50 engine restarts, it will be erased from ECM memory. Intermittent failures may be caused by faulty sensor, connector or wiring. See INTERMITTENTS in TESTS W/O CODES article in this section.
Chevrolet Lumina APV 1993 - DIAGNOSTIC PROCEDURE
Diagnosis of the computerized engine control system should be performed in the following order:
- Ensure all engine systems not related to the computer are operating properly. DO NOT proceed with testing unless all other problems have been repaired. Perform diagnostic circuit check before using trouble code charts. See BASIC TESTING article in this section.
- If trouble codes were displayed (other than Code 12), determine whether codes are hard or intermittent. Hard codes cause Malfunction Indicator Light (MIL) to illuminate continuously with engine running. See HARD OR INTERMITTENT TROUBLE CODE DETERMINATION. For diagnosing hard codes, proceed to appropriate trouble code chart. For diagnosing intermittent codes, proceed to INTERMITTENTS in TESTS W/O CODES article in this section. Exceptions are Code 13, 15, 24, 44 and 45 charts, which can help diagnose intermittent codes.
- If trouble codes were not displayed and a driveability problem exists, refer to SYMPTOMS in TESTS W/O CODES article in this section. From there you will be sent to the appropriate area in SYSTEM/COMPONENT TESTS article in this section.
- After repairs are made, clear trouble codes and perform FIELD SERVICE MODE CHECK in BASIC TESTING article in this section.
Chevrolet Lumina APV 1993 - RETRIEVING CODES (NON-SCAN)
NOTE: The Assembly Line Data Link (ALDL) connector may also be referred to as the Data Link Connector (DLC) in flow charts. This is the same connector.
- Turn ignition on with engine off. Malfunction Indicator Light (MIL) should glow. Locate Data Link Connector (DLC), attached to ECM wiring harness. Most DLCs are located under dash on driver's side of vehicle. For exact location of DLC, see appropriate COMPONENT LOCATIONS illustration in SYSTEM/COMPONENT TESTS article in this section. Turn ignition on. Insert jumper wire from terminal "B" (diagnostic test terminal) to terminal "A" (ground) of DLC. See Fig. 1.
NOTE: Inserting jumper wire into test and ground terminals of DLC with engine running will cause fuel-injected vehicles to enter field service mode and codes will not flash. See FIELD SERVICE MODE in BASIC TESTING article in the ENGINE PERFORMANCE Section. - Malfunction Indicator Light (MIL) should flash codes. Each code is flashed 3 times. If codes DO NOT flash, perform DIAGNOSTIC CIRCUIT CHECK (GASOLINE) in BASIC TESTING article in this section. To exit diagnostic mode, turn ignition off and remove jumper wire from DLC.
Chevrolet Lumina APV 1993 - READING TROUBLE CODES
NOTE: Trouble codes retrieved from ECM/PCM/VCM may be related to either engine or transmission. For engine-related codes, use this article. For transmission-related codes, see G - TRANS. TESTS W/ CODES article in this section. To identify whether codes relate to transmission or engine, see TROUBLE CODE IDENTIFICATION table.
The ECM stores component failure information under a related trouble code which can be recalled for diagnosis and repair. Read trouble codes by counting Malfunction Indicator Light (MIL) flashes or with diagnostic scan tester connected to the Data Link Connector (DLC). The tester is faster, and capable of reading information which would require testing individual ECM and sensor/solenoid connector terminals with a digital voltmeter. See SCAN TESTER DATA table and SCAN TESTER USAGE.
NOTE: When using a scan tester, there is a time delay between serial data updates. For instantaneous response, a digital voltmeter must be used.
If scan tester is not available, MIL flashes can be read by grounding DLC terminal with ignition on and engine off. For example, FLASH, FLASH, pause, FLASH, longer pause, indicates Code 21. The first series of flashes are the first digit of trouble code. The second series of flashes are the second digit of trouble code. Trouble codes are displayed starting with the lowest code. Each code is displayed 3 times and will continue as long as DLC is grounded.
NOTE: Trouble codes will be recorded at various operating times. Some codes require sensor or switch operation for 5 seconds and others may require longer under certain conditions. Some codes may not set in a service bay operational mode.
Chevrolet Lumina APV 1993 TROUBLE CODE IDENTIFICATION
Code Probable Cause 12 (1) No Engine Speed Sensor Reference Pulse 13 (1) Open Oxygen Sensor Circuit 14 (1) CTS Voltage Low (Sensor Or Signal Line Grounded) 15 (1) CTS Voltage High (Sensor Or Signal Line Open) 16 (1) System Voltage High/Low (3.8L) (2) Transmission Speed Error 17 (1) RPM Signal Problem (3.8L) 18 (1) Cam/Crank Error (3.8L) 21 (1) TP Sensor Voltage High (Open Circuit Or Misadjusted TP Sensor) 22 (1) TP Sensor Voltage Low (Circuit Grounded) 23 (1) Intake Air Temperature Sensor Voltage High 24 (3) Vehicle Speed Sensor Circuit Open Or Grounded 25 (1) Intake Air Temperature Sensor Voltage Low 26 (1) Quad-Driver "A" Fault (3.8L) Quad-Driver 1 Fault (4.3L M/T "S" & "T" Pickup) 27 (1) Quad-Driver 2 Fault (4.3L M/T "S" & "T" Pickup) 28 (4) Pressure Switch Manifold Range Circuit Open Or Shorted 31 (1) Park/Neutral Switch Circuit (3.8L) Turbocharger Wastegate Overboost (4.3L Turbo) Engine Speed Control Governor (5.7L "G" Van) Turbocharger Wastegate Overboost (4.3L Turbo) 32 (1) EGR Error (Improper Vacuum Signal) 33 (1) MAP Voltage High (Circuit Open Or Short To Voltage) 34 (1) MAP Voltage Low (Circuit Open Or Short To Ground) MAF Sensor Signal Voltage Low (3.8L) 35 (1) IAC System Fault 36 (1) Shift Control Problem (3.8L) 37 (4) Brake Switch Stuck On (4L60-E) 38 (1) Brake Switch Circuit (3.8L) Knock Sensor Circuit Open (4.3L M/T "S" & "T" Pickup) 38 (4) Brake Switch Stuck Off (4L60-E) 39 TCC Stuck Off ((1) 3.8L & (4) 4L80-E) (1) Knock Sensor Circuit Shorted (4.3L M/T "S" & "T" Pickup) 41 (1) Cam Sensor Circuit (3.8L) 42 (1) EST Circuit Fault 43 (1) ESC Fault 44 (1) Lean Exhaust Indicated 45 (1) Rich Exhaust Indicated 51 (1) Improperly Installed/Faulty PROM/MEM-CAL 52 (4) Long System Voltage High (4L60-E) 52 (1) Fuel CALPAC Missing 53 (3) System Voltage High (Charging System Problem) 53,54 & 55(1) EGR Fault (3.8L) 54 (1) Fuel Pump Circuit Voltage Low 55 (1) Faulty ECM/PCM/VCM 56 (1) Quad-Driver "B" Fault (3.8L) 58 (4) TTS High Temperature (Sensor Or Signal Line Grounded) 59 (4) TTS Low Temperature (Sensor, Connections, Or Wires Open) 61 (1) Cruise Vent Solenoid (3.8L) 62 (1) Cruise Vacuum Solenoid (3.8L) 63 (1) Cruise System Problem (3.8L) 65 (1) Cruise Servo Position (3.8L) 66 (1) Low A/C Refrigerant Charge (3.8L) 66 (4) 3-2 Control Solenoid Fault (4L60-E) 67 (4) TCC Solenoid Circuit Fault (4L60-E) 67 (1) Cruise Engage Switches (3.8L) 68 (4) Overdrive Ratio Error (Engine RPM Greater Than Input Speed) 68 (1) Cruise System Problem (3.8L) 69 (4) Torque Converter Stuck On (4L60-E) 69 (1) A/C Head Pressure Switch (3.8L) 72 (4) VSS Signal Loss (4L60-E) 73 (4) Force Motor (Pressure Control Solenoid) Error 75 (4) System Voltage Low (Charging System Problem) 79 (4) Transmission Fluid Temperature High (4L60-E) 81 (4) QDM Solenoid "B" (2nd-3rd) Current Error 82 (4) QDM Solenoid "A" (1st-2nd) Current Error 83 (4) QDM TCC Solenoid Circuit Fault (4L80-E) 85 (4) Undefined Gear Ratio (4L80-E) 86 (4) Low Gear Ratio (4L80-E) 87 (4) High Gear Ratio (4L80-E)
(1) Engine code covered in this article.
(2) Models equipped with 4L60-E transmission, and 4.3L "S" and "T" series utility vehicles with man. trans.
(3) Common engine and transmission code covered in this article.
(4) Transmission code. For transmission code diagnosis, see appropriate AUTO TRANS DIAGNOSIS article in AUTO TRANS DIAGNOSIS section.
NOTE: Trouble code charts should only be used if Malfunction Indicator Light (MIL) is illuminated (indicating a current problem exists). Exceptions are Code 13, 15, 24, 44 and 45 charts, which may be used to help diagnose intermittent codes. Anytime Code 51, 52 or 55 is displayed with another code, start with 50-series code first and proceed to lower numbered codes.
Chevrolet Lumina APV 1993 - HARD OR INTERMITTENT TROUBLE CODE DETERMINATION
During any diagnostic procedure, determine if codes are due to hard or intermittent failure. Diagnostic charts will not usually help diagnose intermittent codes. To determine hard codes and intermittent codes, proceed as follows:
- MANUALLY enter diagnostic mode. Read and record all stored trouble codes. Exit diagnostic mode and clear trouble codes. See CLEARING TROUBLE CODES.
- Apply parking brake and place transmission in Neutral or Park. Block drive wheels and start engine. MIL should go out. Run warm engine at specified curb idle for 2 minutes and note MIL.
- If MIL comes on, manually enter diagnostic mode. Read and record trouble codes. This reveals hard failure codes. Codes 13, 15, 24, 44, 45 and 55 may require a road test to reset hard failure after trouble codes were cleared.
- If MIL does not come on, all stored trouble codes were intermittent failures. Exceptions are noted under DIAGNOSTIC PROCEDURE.
Chevrolet Lumina APV 1993 - CLEARING TROUBLE CODES
Turn ignition switch to ON position and ground diagnostic test terminal "B" at DLC. See Fig. 1. Turn ignition switch to OFF position and remove ECM fuse from fuse block for 10 seconds. Replace fuse. Remove diagnostic terminal ground lead. Codes may also be cleared using the General Motors Tech 1 scan tester.
Chevrolet Lumina APV 1993 - ECM LOCATION
For ECM locations, see appropriate COMPONENT LOCATIONS illustration in SYSTEM/COMPONENT TESTS article in this section.
Chevrolet Lumina APV 1993 - DIAGNOSTIC MATERIALS Diagnostic Aids
Diagnostic aids (located in many trouble code charts) are provided as additional tips to help with diagnosis when inspected circuit is okay.
Chevrolet Lumina APV 1993 - Field Service Mode Check
Malfunction Indicator Light (MIL) indicates operational mode of engine if DLC is grounded while engine is running. Light response confirms proper fuel system operation and verifies closed loop operation. Clear codes and perform this test after any repair is completed. Field service mode check can be found by proceeding to FIELD SERVICE MODE CHECK in BASIC TESTING article in this section.
Chevrolet Lumina APV 1993 - SPECIAL TOOLS (DIAGNOSTIC)
NOTE: A special scan tester, plugged into the DLC, can read trouble codes, check system voltages on the serial data line and save a great deal of time. For additional information, see tester owner's manual. Also, see SCAN TESTER USAGE and SCAN TESTER DATA.
The computerized engine control system is most easily diagnosed using a scan tester. However, other tools may aid in diagnosing problems if a scan tester is unavailable. These tools are a tachometer, test light, ohmmeter, digital voltmeter with 10-megohm input impedance (minimum), vacuum pump, vacuum gauge, fuel injector test lights and 6 jumper wires 6" long (one wire with female connectors at both ends, one wire with male connector at both ends and 4 wires with male and female connectors at opposite ends). A test light, rather than a voltmeter, must be used when indicated by a diagnostic chart.
Chevrolet Lumina APV 1993 - SCAN TESTER USAGE
NOTE: Before connecting scan tester, check diagnostic system and ensure accurate information is received by scan tester. Perform DIAGNOSTIC CIRCUIT (GASOLINE) CHECK in BASIC TESTING article in this section. If vehicle does not pass diagnostic circuit check, information received by scan tester may be invalid.
The scan tester is a specialized tester which can diagnose on-board computer control systems by providing almost instant access to circuit voltage information without crawling under dash or hood to backprobe sensors and connectors. scan testers reduce diagnostic time by furnishing input data (voltage signals) which can be compared to specification parameters. See SCAN TESTER DATA table.
Scan testers also furnish information on output device (solenoids and motors) status. However, status parameters are only an indication output signals have been sent to devices by the ECM. They do not indicate whether devices respond properly to that signal. This must be verified at output device using a voltmeter or test light.
NOTE: Code 12 should always exist when DLC test terminal is grounded with key on and engine off, but it may not be indicated by all makes of scan tester.
If trouble codes are not present, a problem may still exist. Driveability-related problems with codes displayed occur about 20 percent of the time, while driveability problems without codes occur about 80 percent of the time. Out-of-calibration sensors WILL NOT set a trouble code, but WILL cause driveability problems. A scan tester is the easiest method of checking sensor specifications and other data parameters. Tester is also useful in finding intermittent wiring problems by wiggling wiring harnesses and connections (key on, engine off) while observing data parameters. See SCAN TESTER DATA table.
NOTE: Information obtained by scan tester is only as accurate as the tester itself. If erroneous voltage signals are suspected, verify tester information using a digital voltmeter and wiring schematic. If non-existent codes are displayed, turn ignition off and remove tester. Turn ignition on and ground DLC test terminal. If same codes are not flashed by Malfunction Indicator Light (MIL) as were indicated by scan tester, tester cannot be used on vehicle and information obtained by it will not be guaranteed accurate.
Chevrolet Lumina APV 1993 - SCAN TESTER DATA
NOTE: Information contained in the following table is typical of readings taken on vehicle with engine idling, upper radiator hose hot, throttle closed, transmission in Park or Neutral, closed loop status achieved and all accessories off (except as noted in tables). Not all devices and systems are used on all models. For additional information, see tester owner's manual.
Chevrolet Lumina APV 1993 SCAN TESTER DATA
Tester Position Units Measured Nominal Value A/C Clutch On/Off Off (On With A/C) A/C Request Yes/No No/Yes (With Request) Battery Voltage Volts 13.5-14.5 Block Learn Counts 118-138 (128 Normal) Clear Flood On/Off See Tester Manual Coolant Temp. ?C 85-105? (Norm. Temperature) Crank RPM RPM 100-900 Cross Counts Counts 0-255 Desired RPM RPM ECM Desired RPM EGR Duty Cycle 0-100% 0/Closed-100/Fully Open IAC Counts 0-50 Injector Pulse Width Mil./Sec .8-3.0 INT (Integrator) Counts 110-145 (128 Normal) Knock Retard (ESC) Counts 0-255 Knock Signal Yes/No Yes When Knock Exists MAT ?C 10-90? MAP Volts 1 (idle) To 4.5 (WOT) Open/Closed Loop Status Ol/Cl Closed/Open During Extended Idle Oxygen Sensor Millivolts 100 (Lean) To 999 (Rich) P/N Switch P/N/RDL Park/Neutral P/S Switch Norm/Hi Normal PROM I.D. PROM # Original Factory Number RPM RPM Spec. +/-25 RPM Drive (A/T) RPM RPM Spec. +/-50 RPM Neut. (M/T) TCC On/Off Off (On With Command) TPS Volts 1.25 (Idle) To 5.0 (WOT) Throttle Angle 0-100% 0 (Idle) To 100 (WOT) Trouble Codes Code # No codes Upshift Light(Man. Trans.) On/Off Off VSS Or MPH MPH 0-Actual 4th Gear Switch On/Off On/4th Gear
Chevrolet Lumina APV 1993 - SUMMARY
If hard fault codes are not present and driveability symptoms or intermittent codes exist, proceed to TESTS W/O CODES article in this section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.), or intermittent diagnostic procedures.
Chevrolet Lumina APV 1993 - SELF-DIAGNOSTIC TESTS
NOTE: The following diagnostic flow charts and mini-schematics are supplied courtesy of General Motors Corp.
Chevrolet Lumina APV 1993 - CODE 13, OPEN OXYGEN SENSOR CIRCUIT
When exhaust temperature is less than 600?F (316?C), O2 sensor is open and produces no voltage. An open sensor circuit or cold sensor will not allow system to enter closed loop. On 4.3L engines, oxygen sensor is equipped with an internal heating unit. This allows sensor to reach operating temperature quicker and maintain closed loop operation even during extended idle. Heating element resistance should be 3.5-14 ohms at 662?F (350?C).
NOTE: Test numbers refer to test numbers on diagnostic chart.
- Code 13 will set at normal operating temperature if at least 2 minutes have passed since engine start, Code 21 or 22 is not present, O2 signal voltage is steady at .35-.55 volt and throttle position sensor signal is greater than idle. All conditions must be met for at least one minute.
- This determines if fault is in O2 sensor, ECM or wiring.
- Use only a high-impedance Digital Volt-Ohmmeter (DVOM) while checking for continuity in signal and ground circuits. If ground circuit is open, voltage on signal circuit will be greater than .6 volt.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Verify a clean, tight connection for ground circuit No. 413. An open circuit at sensor signal terminal or ground terminal will result in a Code 13.
Chevrolet Lumina APV 1993 CODE 13 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color All With 4L80-E A/T (1) Oxygen Sensor Signal C14 Purple Oxygen Sensor Ground C13 Tan 2.5L, 2.8L, 3.1L & "C", "K" & "P" Series 4.3L (1) & V8 (All With M/T) Oxygen Sensor Signal D7 Purple Oxygen Sensor Ground D6 Tan 3.8L Oxygen Sensor Signal BD3 Purple Oxygen Sensor Ground BD2 Tan 4.3L (1) "S" & "T" Series Pickup With M/T Oxygen Sensor Signal A9 Purple Oxygen Sensor Ground A7 Tan 4.3L (1) "S" & "T" Series Utility Vehicles With Man. Trans. & All Models With 4L60-E A/T (1) Oxygen Sensor Signal A10 Purple Oxygen Sensor Ground A12 Tan 4.3L (1) Turbo Oxygen Sensor Signal GE14 Purple Oxygen Sensor Ground GE15 Tan
(1) The 4.3L oxygen sensor has 3 wires: sensor signal, common ground and heating element.
Fig. 2: Chevrolet Lumina APV 1993 - Component Locations - CODE 13, Schematic, Oxygen Sensor Circuit
Fig. 3: Chevrolet Lumina APV 1993 - Component Locations - CODE 13, Flowchart, Oxygen Sensor Circuit
Chevrolet Lumina APV 1993 - CODE 14, COOLANT SENSOR SIGNAL VOLTAGE LOW
ECM uses coolant temperature sensor inputs in determining control of fuel delivery, engine timing (EST), idle (IAC) and converter clutch (TCC). As engine warms, sensor resistance reduces. At normal operating temperature, voltage signal will be about .5-1.1 volts (4.3L Turbo) or 1.5-2.0 volts (all other models) at ECM coolant sensor signal terminal.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- This tests if code was set because of a hard failure or intermittent condition. Code 14 sets if signal voltage indicates a coolant temperature greater than 275?F (135?C) for more than 3 seconds on 4.3L Turbo or 6 seconds on all other models. 2) This simulates conditions for a Code 15. If ECM recognizes open circuit by displaying a low temperature, ECM and wiring are not at fault.
Chevrolet Lumina APV 1993 - Diagnostic Aids
After engine is started, temperature should rise steadily to about 194?F (90?C), then stabilize when thermostat opens. If engine is allowed to cool overnight, coolant temperature sensor and MAT sensor (if equipped) should read close to each other, when measured with a scan tester.
Chevrolet Lumina APV 1993 CODE 14 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color All With 4L80-E A/T CTS Signal D16 Yellow CTS Ground D3 Black 2.5L, 3.1L & 4.3L & 5.7L "P" Series With M/T CTS Signal C10 Yellow CTS Ground A11 Black 2.8L & 4.3L & V8 "C" & "K" Series With M/T CTS Signal C10 Yellow CTS Ground D2 Black 3.1L CTS Signal C10 Yellow CTS Ground D2 Black 3.8L CTS Signal BB9 Yellow CTS Ground BA8 Black 4.3L "S//T" Series Pickup With M/T CTS Signal C16 Yellow CTS Ground D2 Black 4.3L "S/T" Series Utility Vehicles With M/T & All Models With 4L60-E A/T CTS Signal B8 Yellow CTS Ground B3 Black 4.3L Turbo CTS Signal GE16 Yellow CTS Ground BB6 Black
Chevrolet Lumina APV 1993 TEMPERATURE-TO-RESISTANCE VALUES(1) (2)
?F (?C) Ohms 210 (100) 177 160 (70) 450 100 (38) 1800 70 (20) 3400 40 (4) 7500 20 (-7) 13,500 0 (-18) 25,000 -40 (-40) 100,700
(1) Measure resistance across sensor terminals.
(2) Values are approximates.
Chevrolet Lumina APV 1993 - CODE 15, COOLANT SENSOR SIGNAL VOLTAGE HIGH
As engine warms, sensor resistance reduces and voltage drops. At normal operating temperature, voltage signal will be about .5-1.1 volts (4.3L Turbo) or 1.5-2.0 volts (all other models) at ECM coolant sensor signal terminal. If sensor signal circuit opens, ECM will see -40?F (-40?C) and deliver fuel for this temperature.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- This checks if code was set as a result of a hard failure or intermittent condition. Code 15 will set if engine is running for more 50 seconds and signal voltage indicates a coolant temperature less than -22?F (-30?C) for more than 30 seconds.
- This simulates conditions for a Code 14. If ECM recognizes grounded circuit and displays a high temperature, ECM and wiring are okay.
- This determines if problem is ECM or wiring. There should be 5 volts present at sensor when measured with a DVOM.
Chevrolet Lumina APV 1993 - Diagnostic Aids
After engine starts, temperature should rise steadily to about 194?F (90?C) and stabilize when thermostat opens. If engine is allowed to cool overnight, coolant temperature sensor and MAT sensor (if equipped) should read close to each other when measured with a scan tester. Code 15 will also set if sensor signal or ground circuit is open.
Chevrolet Lumina APV 1993 CODE 15 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color All With 4L80-E A/T CTS Signal D16 Yellow CTS Ground D3 Black 2.5L, 3.1L & 4.3L & 5.7L "P" Series With M/T CTS Signal C10 Yellow CTS Ground A11 Black 2.8L & 4.3L & V8 "C" & "K" Series With M/T CTS Signal C10 Yellow CTS Ground D2 Black 3.1L CTS Signal C10 Yellow CTS Ground D2 Black 3.8L CTS Signal BB9 Yellow CTS Ground BA8 Black 4.3L "S//T" Series Pickup With M/T CTS Signal C16 Yellow CTS Ground D2 Black 4.3L "S/T" Series Utility Vehicles With M/T & All Models With 4L60-E A/T CTS Signal B8 Yellow CTS Ground B3 Black 4.3L Turbo CTS Signal GE16 Yellow CTS Ground BB6 Black
Chevrolet Lumina APV 1993 TEMPERATURE-TO-RESISTANCE VALUES(1) (2)
?F (?C) Ohms 210 (100) 177 160 (70) 450 100 (38) 1800 70 (20) 3400 40 (4) 7500 20 (-7) 13,500 0 (-18) 25,000 -40 (-40) 100,700
(1) Measure resistance across sensor terminals.
(2) Values are approximates.
Chevrolet Lumina APV 1993 - CODE 16, SYSTEM VOLTAGE HIGH/LOW 3.8L
Control module monitors battery voltage on battery feed circuit. If control module detects battery voltage greater than 17 volts or less than 9 volts for more than 10 seconds, it will set a Code 16 in memory.
NOTE: Test number refers to number on diagnostic chart. Starting engine with battery charger connected may set Code 16.
- Test alternator output to determine proper operation of voltage regulator. Increase engine speed to moderate level. Measure voltage across battery terminals. If reading is more than 17 volts or less than 9 volts, service alternator.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Check for poor connections or damaged harness. Also, check for an intermittent condition by starting engine and wiggling connection while monitoring battery voltage on scan tester. If voltage status changes abruptly or engine stalls, check for loose connections.
NOTE: When Code 16 sets, transaxle will be forced to 3rd gear, preventing erratic shifting due to improper voltage.
Chevrolet Lumina APV 1993 - CODE 16, TRANSMISSION OUTPUT SPEED 4.3L "S" & "T" SERIES UTILITY VEHICLES WITH M/T & 4.3L WITH 4L60E TRANSMISSION
VSS signal buffer supplies 2002 pulses per mile to PCM on vehicle speed signal circuit. Code 16 will set if this signal is lost due to an open or grounded signal line.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- This tests for battery voltage at VSS buffer.
- This tests for proper ground path for VSS buffer.
- This tests for VSS buffer signal to PCM.
- This test checks for faulty connections and a faulty VSS buffer.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Check connections at VSS buffer and PCM. If other codes are set along with Code 16 refer to appropriate code chart for diagnosis and repair.
Chevrolet Lumina APV 1993 - CODE 17, RPM SIGNAL PROBLEM 3.8L
NOTE: Test numbers refer to numbers on diagnostic chart.
- Verifies spark reference circuit is not shorted to ground or open in ignition jumper harness.
- If a window on harmonic balancer is lined up with 18X Hall Effect switch, ignition module will ground spark reference signal. Starter may have to be bumped several times to obtain a voltage reading.
- Voltage reading should be lower than reading obtained with engine not running, indicating a pulsed reference signal.
Chevrolet Lumina APV 1993 - Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside insulation. Also, check for backed-out connector terminals or broken insulation spark reference circuit. If everything checks okay, try wiggling related wiring harness and connectors while engine is idling. This may help to isolate location of malfunction.
Chevrolet Lumina APV 1993 - CODE 18, CAM/CRANK ERROR 3.8L
During cranking, ignition module monitors dual crank sensor sync signal. Sync signal is used to determine correct cylinder pair to spark first. After synch signal has been processed by ignition module, module sends a fuel control reference pulse to PCM. When PCM receives this pulse, it will command all 6 injectors to fire for one priming shot of fuel. After priming, all injectors are held off for 2 crankshaft revolutions to allow cylinder to use fuel from priming shot. After firing, PCM begins to operate injectors in sequential mode based upon true camshaft position. PCM expects to see 6 fuel control pulses for each cam pulse. If sequence of these pulses is incorrect 10 times consecutively, Code 18 will set.
NOTE: Test numbers refer to numbers on diagnostic chart.
- Determines if conditions necessary to set code still exist.
- If 5 volts are not present at PCM harness connector terminal, cam sensor may be interfacing with magnet in camshaft sprocket. Bumping starter should correct this problem.
- If a failure is induced in fuel control reference circuit, 5 volts on circuit should change when faulty wiring or connection is manipulated.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Code 18 indicates an intermittent fault and may not set immediately or under all conditions. Symptoms experienced may help isolate cause of condition. A poor connection or fault in any cam sensor circuit or a faulty cam sensor may cause PCM to re-initialize injector sequence, causing a possible stumble or miss. A poor connection or fault in any crank sensor circuit or fuel control circuit or bent or missing vanes on harmonic balancer interrupter rings will cause PCM to stop pulsing injectors when fault occurs. This will cause an intermittent stumble or stall.
Fig. 14: Chevrolet Lumina APV 1993 - Component Locations - CODE 18, Schematic, Cam/Crank Sensor 3.8L
Fig. 15: Chevrolet Lumina APV 1993 - Component Locations - CODE 18, Flowchart, Cam/Crank Sensor 3.8L
Chevrolet Lumina APV 1993 - CODE 21, TPS SIGNAL VOLTAGE HIGH
Throttle Position Sensor (TPS) provides a varying voltage signal depending on throttle valve angle. Signal voltage varies from about .50 volt at idle to 4.5 volts at wide open throttle. Each time TPS voltage drops to less than 1.25 volts and stops, ECM assumes this is zero degrees throttle angle and measures throttle percentage angle from this point.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- This test confirms Code 21 and checks if fault is a hard failure or an intermittent condition. Code 21 will set if TPS voltage is greater than 2.5 volts 2-10 seconds with engine running. On 2.8L, Code 21 may set if MAP sensor signal less than 2 volts.
- This test simulates conditions for Code 22. If ECM recognizes low voltage signal and sets Code 22, ECM and power and signal circuits are not at fault.
- This step isolates a faulty sensor, ECM or an open ground circuit.
Chevrolet Lumina APV 1993 - Diagnostic Aids
A scan tester displays throttle position in volts. Closed throttle voltage should be less than 1.0 volt (4.3L Turbo) or less than 1.25 volts (all other models). TPS voltage should increase at a steady rate to about 4.5 volts as throttle angle increases. Code 21 will also result if ground circuit is open or TPS signal circuit is shorted to voltage.
Chevrolet Lumina APV 1993 CODE 21 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color All With 4L80-E Transmission TPS Signal C5 Dark Blue TPS Ground D3 Black TPS Reference C4 Gray 2.5L, & 4.3L & 5.7L "P" Series With M/T TPS Signal C13 Dark Blue TPS Ground A11 Black TPS Reference C14 Gray 2.8L, 3.1L, 4.3L & V8 "C" & "K" Series TPS Signal C13 Dark Blue TPS Ground D2 Black TPS Reference C14 Gray 3.8L TPS Signal BB10 Dark Blue TPS Ground BA8 Black TPS Reference BB3 Gray 4.3L "S" & "T" Series Pickup With Man. Trans. TPS Signal C13 Dark Blue TPS Ground D2 Black TPS Reference C8 Gray 4.3L "S/T" Series Utility Vehicles With M/T & All Models With 4L80-E A/T TPS Signal A15 Dark Blue TPS Ground B3 Black TPS Reference F14 Gray 4.3L Turbo TPS Signal GF13 Dark Blue TPS Ground BB5 Black TPS Reference BA5 Gray
Chevrolet Lumina APV 1993 - CODE 22, TPS SIGNAL VOLTAGE LOW
Throttle Position Sensor (TPS) provides a varying voltage signal depending on throttle valve angle. Signal voltage varies from less than about .50 volt at idle to 4.5 volts at wide open throttle.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- This test confirms Code 22 and tests if fault is a hard failure or an intermittent condition. Code 22 will set if engine is running and TPS voltage is less than .2 volt for 2-4 seconds.
- This simulates Code 21. If ECM recognizes a high voltage signal and sets Code 21, ECM and wiring are not at fault. Replace TPS.
- This simulates a high voltage signal to check for on open TPS signal circuit.
Chevrolet Lumina APV 1993 - Diagnostic Aids
A scan tester displays throttle position in volts. Closed throttle voltage should be less than 1.0 volt (4.3L Turbo) or less than 1.25 volts (all other models). TPS voltage should increase at a steady rate to about 4.5 volts as throttle angle increases. Code 22 will also set if TPS signal or ground circuits are open or grounded.
Chevrolet Lumina APV 1993 CODE 22 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color All With 4L80-E Transmission TPS Signal C5 Dark Blue TPS Ground D3 Black TPS Reference C4 Gray 2.5L, & 4.3L & 5.7L "P" Series With M/T TPS Signal C13 Dark Blue TPS Ground A11 Black TPS Reference C14 Gray 2.8L, 3.1L, 4.3L & V8 "C" & "K" Series TPS Signal C13 Dark Blue TPS Ground D2 Black TPS Reference C14 Gray 3.8L TPS Signal BB10 Dark Blue TPS Ground BA8 Black TPS Reference BB3 Gray 4.3L "S" & "T" Series Pickup With Man. Trans. TPS Signal C13 Dark Blue TPS Ground D2 Black TPS Reference C8 Gray 4.3L "S/T" Series Utility Vehicles With M/T & All Models With 4L80-E A/T TPS Signal A15 Dark Blue TPS Ground B3 Black TPS Reference F14 Gray 4.3L Turbo TPS Signal GF13 Dark Blue TPS Ground BB5 Black TPS Reference BA5 Gray
Chevrolet Lumina APV 1993 - CODE 23, MAT SENSOR TEMP. LOW - 3.8L & 4.3L CPI
ECM supplies and monitors a voltage signal (4-6 volts) to sensor. When temperatures are low, sensor resistance is high and ECM will see a high-monitored voltage signal. As temperature increases, sensor resistance decreases and voltage sensed by ECM drops.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- This checks if Code 23 is a hard failure or an intermittent condition. Code 23 will set if engine is running for one minute, MAT sensor temperature is less than -22?F (-30?C) for 12 seconds and speed sensor signal is not present.
- This simulates conditions for a Code 25. If scan tester displays a high temperature, ECM and wiring are not at fault.
- This checks for continuity of sensor signal and ground circuits.
Chevrolet Lumina APV 1993 - Diagnostic Aids
If engine is allowed to cool overnight, coolant and MAT sensors should read close to each other, when measured with a scan tester. A Code 23 will also result if signal and ground circuits become open.
Chevrolet Lumina APV 1993 CODE 23 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color 3.8L Signal BB7 Tan MAT Ground BA7 Black/White 4.3L CPI Signal B9 Tan MAT Ground B4 Purple
Chevrolet Lumina APV 1993 TEMPERATURE-TO-RESISTANCE VALUES(1) (2)
?F (?C) Ohms 210 (100) 185 160 (70) 450 100 (38) 1800 70 (20) 3400 40 (4) 7500 20 (-7) 13,500 0 (-18) 25,000 -40 (-40) 100,700
(1) Measure resistance across sensor terminals.
(2) Temperatures are approximates.
Chevrolet Lumina APV 1993 - CODE 23, MAT SENSOR TEMP. LOW - 4.3L TURBO
ECM supplies and monitors a voltage signal (4-6 volts) to sensor. When temperatures are low, sensor resistance is high and ECM will see a high-monitored voltage signal. As temperature increases, sensor resistance decreases and voltage sensed by ECM drops.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- A scan tester cannot be used to diagnose this fault due to the ECM transmitting a default value when code is set. Code will set due to an open sensor, wire, or connections. This step determines if the wiring and ECM are okay.
- If resistance is greater than 25 k/ohms, replace sensor.
Chevrolet Lumina APV 1993 - CODE 24, VEHICLE SPEED SENSOR - 4.3L TURBO & 4.3L ("C", "K" & "P" SERIES) WITH MANUAL TRANSMISSION
NOTE: The VSS buffer is an internal part of the Digital Ratio Adapter Controller (DRAC) and the terms are used interchangeably.
ECM applies and monitors 12 volts on circuit No. 437. Circuit No. 437 is connected to Digital Ratio Adapter Controller (DRAC) which alternately grounds this circuit when it is receiving voltage pulses from Vehicle Speed Sensor (VSS). Scan tester reading should closely match speedometer reading.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- Code 24 will set if voltage on circuit No. 437 is constant, engine speed is greater than 1200 RPM, vehicle speed is less than 2 MPH, vehicle is not in Park or Neutral and all conditions have been met for at least 5 seconds. These conditions are met during a road load deceleration.
- This determines if DRAC is receiving AC signal from VSS.
- This test monitors DRAC voltage on circuit No. 437. With wheels turning, pulsing voltage should be present. Voltage variation will be greater at a low speed to an average of 4-6 volts at about 20 MPH.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Scan tester reading should closely match speedometer reading with drive wheels turning. If vehicle is equipped with an automatic transmission, check park/neutral switch adjustment. If no problem is found while using flow chart, see INTERMITTENTS in TESTS W/O CODES article in this section.
Fig. 25: Chevrolet Lumina APV 1993 - Component Locations - CODE 24, Schematic, VSS (4.3L Turbo)
Chevrolet Lumina APV 1993 - CODE 24, VEHICLE SPEED SENSOR (VSS) 3.1L
ECM applies and monitors a 12-volt signal on circuit No. 437 to Vehicle Speed Sensor (VSS). VSS is connected to speed sensor buffer which alternately grounds and opens circuit No. 437 when wheels are turning. This pulsing action takes place about 2000 times per mile. Voltage level and pulses increase with vehicle speed. ECM converts pulsing voltage to MPH. ECM uses VSS information in calculations to determine vehicle adjustments. Scan tester reading should closely match speedometer reading when wheels are turning.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- A Code 24 sets when MPH is less than 2 MPH, transmission is not in Park or Neutral, engine speed is greater than 1400 RPM, TPS is greater than 5 percent, circuit No. 437 voltage is constant and all of these conditions are met for 30 seconds. These conditions are met during a road load deceleration.
- A steady 8-12 volts at ECM connector indicates VSS circuit is open or speed sensor is faulty. A voltage of less than one volt at IP connector indicates circuit No. 437 wire is shorted to ground. Disconnect vehicle speed sensor connector. If voltage is now greater than 10 volts, vehicle speed sensor buffer is faulty. If voltage remains less than 8 volts, circuit is grounded. If circuit is not grounded, check for faulty ECM connector or ECM. Before replacing ECM, PROM should be checked for correct application.
Chevrolet Lumina APV 1993 - Diagnostic Aids
A faulty or misadjusted Park/Neutral switch may set a false Code 24. Use scan tester and check for proper signal in Drive, while wiggling shifter. Scan tester MPH reading should closely match speedometer when vehicle is moving. If code is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.
Fig. 27: Chevrolet Lumina APV 1993 - Component Locations - CODE 24, Schematic, VSS (3.1L)
Fig. 28: Chevrolet Lumina APV 1993 - Component Locations - CODE 24 - Flowchart, VSS (3.1L)
Chevrolet Lumina APV 1993 - CODE 24, VEHICLE SPEED SENSOR (VSS) 3.8L
Speed sensor, which is a Permanent Magnet (PM) generator, provides control module with vehicle speed information. PM generator, mounted in transmission, produces a pulsing AC voltage signal whenever vehicle speed is greater than 3 MPH. Voltage level and pulses increase with vehicle speed. Control module converts pulsing voltage to MPH, which is used by control module to calculate vehicle adjustments.
NOTE: Test numbers refer to numbers on diagnostic chart.
- If Code 36 is stored along with Code 24, go to that chart first. PM generator only produces a voltage signal if drive wheels are turning greater than 3 MPH.
- Before replacing control module, MEM-CAL should be checked for correct application.
Chevrolet Lumina APV 1993 - Diagnostic Aids
A faulty or misadjusted park/neutral switch may set a false Code 24. Use scan tester to check for proper signal in Drive while wiggling shifter. Code 24 may set if vehicle is power braked (brakes applied and throttle depressed) for more than 10 seconds. Check circuits No. 400 and 401 for proper connections.
Fig. 29: Chevrolet Lumina APV 1993 - Component Locations - CODE 24, Schematic, VSS (3.8L)
Fig. 30: Chevrolet Lumina APV 1993 - Component Locations - CODE 24, Flowchart, VSS (3.8L)
Chevrolet Lumina APV 1993 - CODE 24, VEHICLE SPEED SENSOR 4.3L "S" & "T" SERIES PICKUP WITH MAN. TRANS. (EXCEPT TURBO) & ALL 4WD WITH 4L80-E TRANSMISSION
VSS output sensor is a magnetic induction type. Gear teeth pressed on outside diameter of output carrier assembly induce an alternating current in sensor when drive wheels are turning. Since vehicle speed is taken from transfer case on 4WD vehicles, output speed sensor signal on these units goes directly to PCM. Code 24 will set if gear selector is not in Park or Neutral, engine speed is at least 3000 RPM and output speed is less than 200 RPM for at least 1.5 seconds.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- Test verifies VSS voltage at PCM.
- Test verifies VSS signal at sensor.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Check all connections, especially those at transmission pass-through connector. If code is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section. While Code 24 is set, scan tester will display an RPM derived from input speed. If input speed sensor is not operational at start-up, this can cause VSS to read zero.
Chevrolet Lumina APV 1993 - CODE 24, VEHICLE SPEED SENSOR 4.3L "S" & "T" SERIES UTILITY VEHICLES WITH MANUAL TRANSMISSION, 4.3L, 5.0L & 5.7L WITH 4L60E TRANSMISSION & ALL 2WD WITH 4L80-E TRANSMISSION
NOTE: The VSS buffer is an internal part of the Digital Ratio Adapter Controller (DRAC) and the terms are used interchangeably.
VSS output sensor circuit consists of a magnetic induction type speed sensor, Digital Ratio Adapter Controller (DRAC), and wiring. Gear teeth pressed on outside diameter of output carrier assembly induce an alternating current in sensor when drive wheels are turning. Signal is transmitted to instrument cluster DRAC where it is converted to a square wave signal which is passed on to PCM, cruise control, speedometer, and anti-lock brake system. Code 24 will set if gear selector is not in Park or Neutral, engine speed is at least 3000 RPM and output speed is less than 200 RPM for at least 1.5 seconds. If input speed sensor is not operational at start-up, this can cause VSS to read zero.
NOTE: Test numbers refer to test numbers on diagnostic chart.
Chevrolet Lumina APV 1993 - Preliminary Steps
Disconnect VSS buffer connector. Connect test light between terminals C8 and C9. Turn ignition on. If test light does not light, repair power or ground circuit to VSS buffer.
- Test verifies VSS voltage at PCM.
- Test verifies VSS signal to DRAC.
- Test verifies VSS signal at sensor.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Check all connections, especially those at transmission pass-through connector. If code is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section. While Code 24 is set, scan tester will display an RPM derived from input speed.
Chevrolet Lumina APV 1993 - CODE 25, MAT SENSOR TEMP. HIGH - 3.8L & 4.3L CPI
ECM applies and monitors a voltage signal (4-6 volts) to MAT sensor. When manifold air is cold, sensor resistance is high and ECM sees a high signal voltage. As air warms, resistance decreases and voltage sensed by ECM drops. Sensor resistance can be measured at sensor terminals with harness disconnected.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- This checks if code is a hard failure or an intermittent condition. Code 25 will set if a VSS signal is present (2.5L) and monitored MAT sensor temperature is greater than 302?F (150?C) for 2.5L or 275?F (135?C) for others.
- This simulates conditions for a Code 23. If scan tester displays a low temperature, ECM and wiring are not at fault.
Chevrolet Lumina APV 1993 - Diagnostic Aids
If engine is allowed to cool overnight, coolant temperature sensor and MAT sensor should read close to each other, when measured with a scan tester. A Code 25 will also result if sensor signal circuit is shorted to ground.
Chevrolet Lumina APV 1993 CODE 25 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color 3.8L Signal BB7 Tan MAT Ground BA7 Black/White 4.3L CPI Signal B9 Tan MAT Ground B4 Purple
Chevrolet Lumina APV 1993 TEMPERATURE-TO-RESISTANCE VALUES(1) (2)
?F (?C) Ohms 210 (100) 185 160 (70) 450 100 (38) 1800 70 (20) 3400 40 (4) 7500 20 (-7) 13,500 0 (-18) 25,000 -40 (-40) 100,700
(1) Measure resistance across sensor terminals.
(2) Temperatures are approximates.
Chevrolet Lumina APV 1993 - CODE 25, MAT SENSOR TEMP. LOW - 4.3L TURBO
ECM supplies and monitors a voltage signal (4-6 volts) to sensor. When temperatures are low, sensor resistance is high and ECM will see a high-monitored voltage signal. As temperature increases, sensor resistance decreases and voltage sensed by ECM drops.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- A scan tester cannot be used to diagnose this fault due to the ECM transmitting a default value when code is set. If voltage is greater than 4 volts, wiring and ECM are okay.
- If resistance is less than 100 ohms, replace sensor.
Chevrolet Lumina APV 1993 TEMPERATURE-TO-RESISTANCE VALUES(1) (2)
?F (?C) Ohms 210 (100) 185 160 (70) 450 100 (38) 1800 70 (20) 3400 40 (4) 7500 20 (-7) 13,500 0 (-18) 25,000 -40 (-40) 100,700
(1) Measure resistance across sensor terminals.
(2) Temperatures are approximates.
Chevrolet Lumina APV 1993 - CODE 26, QUAD-DRIVER CIRCUIT 3.8L
Each PCM Quad-Driver Module (QDM) has a fault line which is monitored by PCM. PCM compares voltage values of fault line with acceptable values in PCM memory. If PCM senses values other than accepted values, a Code 26 will set.
Some QDM circuits will normally cycle between high and low, such as when brake pedal is depressed. Some scan testers may set a false Code 26 if engine is running, tester is installed and brake pedal is depressed for more than 30 seconds.
NOTE: Test number refers to number on diagnostic chart.
- PCM does not know which controlled circuit set Code 26, so this chart checks each circuit to determine which is at fault. This step tests SERVICE ENGINE SOON light driver and circuit.
- This determines which circuit is out of specification.
Chevrolet Lumina APV 1993 - QDM Symptoms:
- Puller fan on all the time or will not come on at all.
- TCC does not engage.
- Poor driveability due to 100 percent canister purge.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Monitor voltage of each terminal while moving related harness connectors, including PCM harness. If fault is induced, voltage will change. This may help locate intermittent problems. If code reappears with no apparent problems, replace PCM.
Chevrolet Lumina APV 1993 - CODE 26, QUAD-DRIVER CIRCUIT 3.8L
NOTE: Test number refers to number on diagnostic chart.
This determines if problem is circuit or component. Factory-installed PCM has an internal fuse and is unlikely to need replacement.
Chevrolet Lumina APV 1993 - CODE 26, QUAD-DRIVER NO. 1 CIRCUIT - 4.3L "S" & "T" SERIES PICKUP WITH MANUAL TRANSMISSION
Each PCM Quad-Driver Module (QDM) has a fault line which is monitored by PCM. PCM compares voltage values of fault line with acceptable values in PCM memory. If PCM senses values other than accepted values, a Code 26 will set.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Intermittent faults must be continuously present for 200 milliseconds to cause Code 26 to set. QDM-controlled circuits should be inspected for poor terminal contact or damaged harnesses. QDM faults can be detected when outputs are on or off as follows:
- Open circuit or control circuit shorted to ground - output commanded off.
- Shorted device or control circuit shorted to voltage - output commanded on.
Chevrolet Lumina APV 1993 - CODE 27, QUAD-DRIVER NO. 2 CIRCUIT - 4.3L "S" & "T" SERIES PICKUP WITH MANUAL TRANSMISSION
Each PCM Quad-Driver Module (QDM) has a fault line which is monitored by PCM. PCM compares voltage values of fault line with acceptable values in PCM memory. If PCM senses values other than accepted values, a Code 27 will set.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Intermittent faults must be continuously present for 200 milliseconds to cause Code 26 to set. QDM-controlled circuits should be inspected for poor terminal contact or damaged harnesses. QDM faults can be detected when outputs are on or off as follows:
- Open circuit or control circuit shorted to ground - output commanded off.
- Shorted device or control circuit shorted to voltage - output commanded on.
Chevrolet Lumina APV 1993 - CODE 31, PARK/NEUTRAL SWITCH CIRCUIT - 3.8L
NOTE: Complete diagnosis of Code 31 for 3.8L requires GM Tech 1 scan tester, which is capable of indicating status of all 4 park/neutral switch positions. This chart does not apply to 3.8L (VIN L) "C", "E" and "H" body vehicles. Schematics for these models are supplied for reference purposes only.
Park/neutral switch contacts are part of neutral start switch. Contacts close to ground in Park or Neutral and open in Drive. Code 31 will set if park/neutral signal circuit indicates an open for 3 consecutive starts or if conditions occur as follows with ignition on and engine off.
- Vehicle speed is zero MPH.
- Gear selector switch indicates a gear other than Park or Neutral.
- Gear selector status indicates an incorrect combination of LO and HI for more than 10 seconds.
Code 31 does not turn on SERVICE ENGINE SOON light.
NOTE: Test numbers refer to numbers on diagnostic chart.
- This tests for proper operation of gear selector switch.
- This tests for proper operation of gear selector switch.
- Tests for an open of grounded circuit.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Check for poor connections or damaged harness. Monitor scan tester status for gear selector switch while wiggling harness.
Chevrolet Lumina APV 1993 - CODE 31, TURBO OVERBOOST - 4.3L TURBO
On turbocharged engines, exhaust gases pass from exhaust manifold through turbocharger, turning turbine blades. Compressor side of turbocharger also turns, pulling air through air filter and pushing it into intake manifold under pressure.
Wastegate is normally closed, but will open to by-pass exhaust gases when an overboost condition exists. This is determined through monitored MAP sensor signals. Under normal driving conditions, ECM energizes wastegate control (solenoid) valve. This blocks off intake manifold pressure from wastegate actuator diaphragm. When overboost condition exists, ECM will de-energize wastegate control (solenoid) valve, allowing intake manifold pressure to act upon actuator diaphragm, opening wastegate.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- Code 31 will set when Code 33 is not set and excessive manifold boost pressure is sensed for 2 seconds. This step tests ability of actuator to open wastegate. Code 31 may be caused by circuit No. 471 shorted to ground, a sticking wastegate or actuator, control (solenoid) valve stuck in closed position, a cut or pinched hose, or a faulty ECM.
- After pressure is applied to valve and then removed, actuator should slowly close wastegate. If not, vent in control (solenoid) valve could be plugged.
- With ignition on and ALDL test terminal "B" grounded, control (solenoid) valve should be energized. This closes off manifold to wastegate actuator.
- This checks electrical control portion of system. With ignition on and engine not running, solenoid should not be energized.
Chevrolet Lumina APV 1993 - CODE 32, EGR SYSTEM ERROR - 3.1L
EGR vacuum is regulated by an ECM-controlled, normally closed solenoid. ECM will turn EGR on and off (duty cycle) by grounding and ungrounding solenoid drive circuit. Duty cycle is calculated by ECM based on coolant temperature, airflow and engine RPM. ECM will check EGR operation when vehicle speed is greater than 50 MPH, MAP is within calibrated range, throttle angle is 8-30 percent and throttle angle is constant. With ignition on and engine stopped, EGR solenoid is de-energized. Grounding ALDL test terminal should energize solenoid, allowing vacuum to pass through to EGR valve.
NOTE: Test numbers refer to numbers on diagnostic chart.
- To check for plugged intake passage, turn ignition off. Remove EGR valve from intake. Plug exhaust side passage with a suitable stopper. With intake side open, attempt to start engine. If engine runs at a very high idle (up to 3000 RPM is possible) or starts and stalls, EGR intake passage is not plugged. If engine starts and idles normally, intake passage is plugged. To check for plugged exhaust passage, with EGR valve still removed, plug intake passage with a suitable stopper. Start engine. If no exhaust gas is present, passage is plugged.
- By grounding ALDL test terminal "B", EGR solenoid should energize, allowing vacuum to pass through solenoid. Vacuum may slowly bleed off. What is important is that vacuum passes through solenoid.
- When the ALDL test terminal "B" is ungrounded, vacuum should bleed off through a vent in the solenoid valve. What is important is that vacuum no longer exists on EGR side of solenoid.
- This test will determine if the electrical control part of the system is at fault or if the connector or solenoid valve is at fault.
- The remaining test checks the ability of the EGR valve to interact with exhaust system. This is a negative backpressure EGR valve which should hold vacuum with engine off.
- When engine is started, vacuum should vent and EGR valve should seat.
Chevrolet Lumina APV 1993 - Diagnostic Aids
The EGR system may become inoperative if the park/neutral switch is out of adjustment.
Chevrolet Lumina APV 1993 - CODE 32, EGR SYSTEM ERROR - 4.3L "G" SERIES, 4.3L "C", "K" & "M" SERIES (NON-CALIFORNIA) WITH 4L60E TRANSMISSION & 4.3L "C", "G", "K" & "P" SERIES WITH 4L80-E TRANSMISSION
PCM controls a solenoid regulating vacuum to EGR valve. Normally closed solenoid prevents vacuum from passing until it is energized by PCM. A properly operating EGR will directly affect fuel integrator counts. With EGR valve open, integrator counts will be less than without EGR operation. If monitored integrator counts do not change with EGR commanded, Code 32 will set.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- When test terminal "B" of ALDL connector is grounded, EGR solenoid should be energized, allowing vacuum to EGR valve. Vacuum should hold.
- When jumper wire is removed from terminal "B", vacuum to EGR valve should bleed through a vent in solenoid and EGR valve should close. Vacuum gauge may or may not bleed off vacuum. However, this does not indicate a problem.
- Determines if fault lies in electrical control part of system, connector or solenoid.
- This system uses a negative backpressure EGR valve. Valve should hold vacuum with engine off.
- When engine is started, backpressure should cause vacuum to bleed off and valve should fully close.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Prior to replacing PCM, check resistance of all PCM-controlled solenoids and relays. Replace any with a resistance value less than 20 ohms.
Chevrolet Lumina APV 1993 - CODE 32, EGR SYSTEM ERROR 4.3L "S" & "T" SERIES UTILITY VEHICLES WITH MANUAL TRANSMISSION (EXCEPT CPI)
PCM controls a solenoid that regulates vacuum to EGR valve. The normally closed solenoid prevents vacuum from passing until it is energized by PCM. A properly operating EGR will directly affect fuel integrator counts. With EGR valve open, integrator counts will be less than without EGR operation. If monitored integrator counts do not change with EGR commanded, Code 32 will set.
ECM checks EGR operation when engine speed is greater than 1600 RPM, MAP sensor signal indicates cruise condition and throttle position are constant.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- With ignition on and engine off, solenoid should not be energized or allow vacuum to pass to EGR valve. When test terminal "B" of ALDL connector is grounded, EGR solenoid should be energized, allowing vacuum to EGR valve. Vacuum should hold.
- Checks for plugged EGR passages. If passages are plugged, engine may have severe detonation on acceleration.
- Vehicle must be driven during this test to produce sufficient load to operate EGR. Lightly accelerating (approximately 1/4 throttle) will produce a large and stable enough reading to determine if ECM is commanding system on.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Prior to replacing PCM, check resistance of all PCM-controlled solenoids and relays. Replace any with a resistance value less than 20 ohms.
Chevrolet Lumina APV 1993 - CODE 32, EGR SYSTEM ERROR - 4.3L "C", "K" & "P" SERIES) & 4.3L "S" & "T" SERIES PICKUP (EXCEPT TURBO) WITH MANUAL TRANSMISSION
ECM controls a solenoid that regulates vacuum to EGR valve. The normally closed solenoid prevents vacuum from passing until it is energized by ECM. A properly operating EGR will directly affect fuel integrator counts. With EGR valve open, integrator counts will be less than without EGR operation. If monitored integrator counts do not change with EGR commanded, Code 32 will set.
ECM checks EGR operation when vehicle speed is greater than 50 MPH, engine vacuum indicates cruise and throttle position are steady.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- With ignition on and engine off, solenoid should not be energized or allow vacuum to pass to EGR valve. When test terminal "B" of ALDL connector is grounded, EGR solenoid should be energized, allowing vacuum to EGR valve. Vacuum should hold.
- Checks for plugged EGR passages. If passages are plugged, engine may have severe detonation on acceleration.
- SERVICE ENGINE SOON light should also flash while diagnostic terminal is grounded. If light does not flash, this may indicate Quad-Driver has been damaged by low TCC circuit resistance.
- Vehicle must be driven during this test to produce sufficient load to operate EGR. Lightly accelerating (approximately 1/4 throttle) will produce a large and stable enough reading to determine if ECM is commanding system on.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Prior to replacing PCM, check resistance of all PCM-controlled solenoids and relays. Replace any solenoids or relays with a resistance value less than 20 ohms.
Chevrolet Lumina APV 1993 - CODE 32, EGR SYSTEM ERROR - 4.3L TURBO
ECM controls a solenoid that regulates vacuum to EGR valve. The normally closed solenoid prevents vacuum from passing until it is energized by ECM. A properly operating EGR will directly affect fuel integrator counts. With EGR valve open, integrator counts will be less than without EGR operation. If monitored integrator counts do not change with EGR commanded, Code 32 will set.
Diagnostic chart covers checks for entire EGR system. If no trouble is found while performing chart routine, fault is an intermittent electrical problem or a sticky EGR valve.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Vacuum switch in EGR solenoid is not used. If EGR valve sticks open, a rough idle will result. If EGR solenoid vent filter becomes plugged, EGR valve will remain open or close slowly. An inoperative check valve in ported vacuum supply line will result in faulty EGR system operation.
Chevrolet Lumina APV 1993 - CODE 32, EGR SYSTEM ERROR - 4.3L WITH LINEAR EGR
ECM regulates linear EGR valve to control exhaust gas recirculation by providing a ground control for internal pintle (solenoid). Pintle will pull away from its seat when energized. ECM controls linear EGR valve based upon coolant temperature and throttle position.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- Checks pintle's ability to be commanded to desired position.
- Checks for voltage to linear EGR valve to verify if problem is in ignition feed circuit.
- Checks ECM control circuit by jumpering across circuits No. 435 and 439 with a test light and grounding ALDL test terminal "B" to command EGR on.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Before replacing ECM, use an ohmmeter and check EGR valve resistances. Resistance between terminals "A" and "E" should be 9.5-10.5 ohms. Resistance between terminals "B" and "D" should be greater than 3000 ohms. Resistance between terminals "B" and "C" should start at 700 ohms and increase to about 4000 ohms as pintle is slowly moved inward.
Chevrolet Lumina APV 1993 - CODE 33, MAP SENSOR SIGNAL VOLTAGE HIGH
Manifold Absolute Pressure (MAP) sensor responds to changes in manifold pressure (vacuum). If MAP sensor fails, ECM will substitute a fixed MAP value and use TPS input to control fuel delivery.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- This test confirms Code 33 and determines if it is a hard failure or an intermittent condition. Code 33 will set when voltage signal reading is too high and TPS voltage indicates throttle is closed.
- This step simulates conditions for a Code 34. If ECM recognizes and indicates low MAP signal, ECM and 5-volt reference and MAP signal circuits are not at fault.
Chevrolet Lumina APV 1993 - Diagnostic Aids
With ignition switch in ON position and engine off, manifold pressure is equal to atmospheric pressure and signal voltage is high. Comparing BARO readings from a known good vehicle using the same sensor is a good way to check accuracy of suspected sensor. Readings should be within .4 volt of each other. Code 33 will also result if ground circuit is open or MAP signal circuit is shorted to voltage or to 5-volt reference circuit.
Chevrolet Lumina APV 1993 CODE 33 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color All With 4L80-E Transmission MAP Signal C10 Light Green MAP Ground D2 Purple MAP Reference D4 Gray 2.8L, 3.1L & 4.3L & V8 "C" & "K" Series MAP Signal C11 Light Green MAP Ground A11 Purple MAP Reference C14 Gray 4.3L & 5.7L "P" Series MAP Signal C11 Light Green MAP Ground D2 Purple MAP Reference C14 Gray 4.3L "S" & "T" Series Pickup With M/T MAP Signal C14 Light Green MAP Ground D3 Purple MAP Reference C9 Gray 4.3L "S/T" Series Utility Vehicles With M/T & All Models With 4L60-E A/T MAP Signal B13 Light Green MAP Ground B4 Purple MAP Reference E14 Gray 4.3L Turbo MAP Signal GF15 Light Green MAP Ground BB6 Black MAP Reference BA4 Gray
Chevrolet Lumina APV 1993 - CODE 34, MAP SENSOR SIGNAL VOLTAGE LOW
Manifold Absolute Pressure (MAP) sensor responds to changes in manifold pressure (vacuum). If MAP sensor fails, ECM will substitute a fixed MAP value and use TPS input to control fuel delivery.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- This confirms Code 34 and determines if code was a hard failure or an intermittent condition. Code 34 will set when ignition is on and MAP signal voltage is low. On some systems, engine must be running to set code.
- Jumpering harness 5-volt reference circuit and MAP signal circuit terminals will determine if problem is sensor, ECM or wiring. If ECM recognizes and indicates high MAP signal, ECM and wiring are okay.
- Scan tester may not display 12 volts. The important thing is that the ECM recognizes voltage as greater than 4 volts (high MAP voltage signal), indicating ECM and MAP signal circuit are not at fault.
Chevrolet Lumina APV 1993 - Diagnostic Aids
With ignition switch in ON position and engine off, manifold pressure is equal to atmospheric pressure and signal voltage will be high. Comparing BARO readings with a known good vehicle using the same sensor is a good way to check accuracy of suspected sensor. Readings should be within .4 volt of each other. A Code 34 will also result if 5-volt reference and MAP signal circuits are open or shorted to ground. If 5-volt reference circuit is not shorted to ground and a Code 22 is stored, check MAP signal circuit for short to ground.
Chevrolet Lumina APV 1993 CODE 34 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color All With 4L80-E Transmission MAP Signal C10 Light Green MAP Ground D2 Purple MAP Reference D4 Gray 2.8L, 3.1L & 4.3L & V8 "C" & "K" Series MAP Signal C11 Light Green MAP Ground A11 Purple MAP Reference C14 Gray 4.3L & 5.7L "P" Series MAP Signal C11 Light Green MAP Ground D2 Purple MAP Reference C14 Gray 4.3L "S" & "T" Series Pickup With Man. Trans. MAP Signal C14 Light Green MAP Ground D3 Purple MAP Reference C9 Gray 4.3L "S/T" Series Utility Vehicles With M/T & All Models With 4L60-E A/T MAP Signal B13 Light Green MAP Ground B4 Purple MAP Reference E14 Gray 4.3L Turbo MAP Signal GF15 Light Green MAP Ground BB6 Black MAP Reference BA4 Gray
Chevrolet Lumina APV 1993 - CODE 34, MAF SENSOR SIGNAL VOLTAGE LOW - 3.8L
Code 34 is set when engine is running without MAF sensor signal for greater than 4 seconds. If Code 34 is set, control module will substitute a value for MAF based upon RPM, TPS and IAC monitored parameters.
NOTE: Test numbers refer to numbers on diagnostic chart.
- Determines if code is result of an intermittent or hard failure.
- Voltage reading at sensor harness terminal "A" of less than 4 volts or more than 6 volts indicates fault in circuit No. 492 or poor connections.
- Verifies both ignition voltage and a good ground are available.
Chevrolet Lumina APV 1993 - Diagnostic Aids
MAF sensor produces a frequency signal, which cannot be easily measured. Check for following:
- Poor Connections - Inspect control module MAF signal pins and harness connectors for backed-out terminals, improper connector mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connection.
- Harness - Inspect MAF sensor harness to ensure it is not too close to high voltage wires, such as spark plug wires.
- Intermittents - If harness appears okay, use scan tester to check MAF while moving related connectors and wiring harness. A change in display would indicate intermittent fault location.
Chevrolet Lumina APV 1993 - CODE 35, IDLE SPEED ERROR
Code 35 will set when closed throttle engine speed is 150 RPM greater or less than correct idle speed for 20 seconds.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- IAC driver is used to extend and retract IAC valve. Movement is verified by changing engine speed. If no engine speed change occurs, valve can be retested when removed from throttle body.
- Checks IAC movement quality from step 1). Between 700-1500 RPM, engine speed should change smoothly with each tester light flash while extending or retracting. If IAC valve is retracted beyond control range (about 1500 RPM), it may take many flashes in extend position before engine speed reduces. This is normal on some engines. Fully extending IAC may cause engine to stall. This may be normal.
- Steps 1) and 2) verified proper IAC valve operation. This step checks IAC circuits. Each light on node light should flash Red and Green, while IAC valve is cycled. While color sequence is not important, if either light is off or does not flash Red and Green, check circuits beginning with poor terminal contacts.
Chevrolet Lumina APV 1993 - IAC VALVE RESET PROCEDURE
Turn ignition off for 10 seconds. Start and run engine for 5 seconds. Turn ignition off another 10 seconds.
Chevrolet Lumina APV 1993 - Diagnostic Aids
A slow, unstable idle may be caused by a system problem that cannot be overcome by IAC. Scan counts will be greater than 60 if too low, and zero counts if too high. If idle is too high, stop engine. With ignition on, ground ALDL test terminal "B". Wait 45 seconds for IAC to seat, then disconnect IAC. Start engine. If idle speed is greater than 800 RPM, inspect vehicle for vacuum leaks.
Chevrolet Lumina APV 1993 - System Too Lean
If air/fuel ratio is too lean, idle speed may be either too high (check for vacuum leaks) or too low. Engine speed may vary and disconnecting IAC may not help. Scan tester and/or digital voltmeter (10 megohm) will read an oxygen sensor output less than 300 mv (.3 volt). Check for low fuel pressure or water in fuel.
Chevrolet Lumina APV 1993 - System Too Rich
If air/fuel ratio is too rich, idle speed will be too low and scan tester counts will usually be greater than 80. The system may be obviously rich with Black smoke from tailpipe. Scan tester and/or voltmeter will read an oxygen sensor voltage signal fixed greater than 800 mv (.8 volt). Look for high fuel pressure or leaking/sticky injectors. Remove IAC and inspect bore for foreign material or evidence of IAC valve dragging bore. A silicone-contaminated oxygen sensor will produce lean air/fuel mixture. Oxygen sensor output would be fixed greater than 800 mv (.8 volt). This may also set Code 45.
Chevrolet Lumina APV 1993 - Throttle Body
Remove IAC and inspect bore for evidence of IAC valve dragging.
Chevrolet Lumina APV 1993 - IAC Valve Connections
Carefully inspect connections for looseness or corrosion.
Chevrolet Lumina APV 1993 - PCV Valve
The wrong PCV valve may cause incorrect idle speed.
Chevrolet Lumina APV 1993 CODE 35 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color 4.3L "S/T" Series Utility Vehicles With M/T & 4.3L, 5.0L & 5.7L With 4L60E A/T "A" Coil High A3 Light Blue/White "A" Coil Low A6 Light Blue/Black "B" Coil High A8 Light Green/White "B" Coil Low A7 Light Green/Black 4.3L Turbo "A" Coil High GE6 Light Blue/White "A" Coil Low GE5 Blue/Black "B" Coil High GE4 Light Green/White "B" Coil Low GE3 Light Green/Black
Fig. 74: Chevrolet Lumina APV 1993 - Component Locations - CODE 35, Schematic, Idle Speed Error
Fig. 75: Chevrolet Lumina APV 1993 - Component Locations - CODE 35, Flowchart, Idle Speed Error
Chevrolet Lumina APV 1993 - CODE 36, SHIFT CONTROL PROBLEM - 3.8L
4T60E transaxle is electronically shifted. Within transaxle are 4 solenoids. Solenoid "A" is used for 1st and 4th gear operation only. Solenoid "B" is used for 1st and 2nd gear operation. Remaining 2 solenoids are for TCC operation only. All PRNDL indications are ignored as far as transaxle shifting is concerned except manual low. Code 36 will set if solenoid "B" failed in OFF position, which will cause transaxle to be in 4th gear, and desired gear is 1st, TPS is greater than 40 percent, engine speed is greater than 2000 RPM, VSS is 3-20 MPH and Codes 21, 22 and 24 are not present. Code will also set if solenoid "B" failed in ON position, which will cause transaxle to be in 1st gear, and desired gear is 4th, PRNDL is in 3rd or 4th, TPS is greater than 10 percent and Codes 31, 21 and 22 are not present. Code 36 does not turn on SERVICE ENGINE SOON light.
Chevrolet Lumina APV 1993 - Diagnostic Aids
When Code 36 is set, transaxle will be forced into 3rd gear. If code sets due to a grounded circuit No. 1223, only 1st and 2nd gear operation will be available. If circuit No. 1223 is open, only 3rd and 4th gear operation will be available. If fault goes away, normal operation will be resumed for duration of key cycle.
Chevrolet Lumina APV 1993 - CODE 38, BRAKE SWITCH CIRCUIT - 3.8L
Code 38 will set if Code 24 is not present, status at brake input terminal of control module has not changed from high to low and vehicle speed has been greater than 35 MPH and back to zero MPH a precalibrated number of times.
NOTE: Test numbers refer to numbers on diagnostic chart.
- Jumpering brake switch determines if ECM and wiring for brake switch are okay.
- Determines if brake switch is out of adjustment or is faulty.
- Verifies voltage to brake switch.
Chevrolet Lumina APV 1993 - Diagnostic Aids
A Code 38 in conjunction with a Code 26 would mean a problem with one or more of following components:
- Fuse or power supply circuit, brake switch or wire before splice.
- Code 38 alone is result of a wire or circuit problem between splice and control module, poor connection to control module, or possibly control module itself.
If brake switch has failed in an open state, TCC will not engage. When code is set TCC will not engage and PCM will not allow 4th gear. Code 38 does not turn on SERVICE ENGINE SOON light on all models.
Chevrolet Lumina APV 1993 - CODE 38, KNOCK SENSOR CIRCUIT OPEN - 4.3L "S" & "T" SERIES PICKUP WITH MANUAL TRANSMISSION
NOTE: Test numbers refer to numbers on diagnostic chart.
- VCM applies and monitors 5 volts on knock signal circuit. This voltage should be present on sensor leads with sensors disconnected.
- Determines if wiring or knock sensor portion of the VCM's internal PROM (MEM-CAL) is faulty
- An improperly installed knock sensor can prevent knock sensor from grounding to block.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Check circuit for potential open. Also, check for proper installation of PROM (MEM-CAL).
Chevrolet Lumina APV 1993 - CODE 39, TCC CIRCUIT - 3.8L
Code 39 will set when TCC is commanded on, vehicle speed is greater than 35 MPH, throttle angle is greater than 10 percent, vehicle is in 3rd or 4th gear, Engine RPM-to-vehicle speed indicates TCC is not locked and all conditions have existed for more than 10 seconds. Code 39 does not turn on SERVICE ENGINE SOON light.
NOTE: Test numbers refer to numbers on diagnostic chart.
- With ALDL test terminal grounded, PCM provides a ground for solenoid. This step tests for power to solenoid.
- Tests to see if problem is faulty solenoid, power supply or driver circuit.
- Tests TCC solenoid driver circuit at PCM.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Scan tester only indicates when PCM has commanded TCC on. This does not indicate TCC is actually engaged. To determine if TCC is engaging, road test vehicle. Engine RPM should decrease when scan tester indicates TCC engagement.
Fig. 83: Chevrolet Lumina APV 1993 - Component Locations - CODE 39, Schematic, TCC Circuit (3.8L)
Fig. 84: Chevrolet Lumina APV 1993 - Component Locations - CODE 39, Flowchart, TCC Circuit (3.8L)
Chevrolet Lumina APV 1993 - CODE 39, KNOCK SENSOR CIRCUIT SHORTED - 4.3L "S" & "T" SERIES PICKUP WITH MANUAL TRANSMISSION
NOTE: Test numbers refer to numbers on diagnostic chart.
- VCM applies and monitors 5 volts on knock signal circuit. This voltage should be present on sensor leads with sensors disconnected.
- Determines if wiring or knock sensor portion of the VCM's internal PROM (MEM-CAL) is faulty
- An improperly installed knock sensor can prevent knock sensor from grounding to block.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Check circuit for potential short to ground. Also, check for proper installation of PROM (MEM-CAL).
Chevrolet Lumina APV 1993 - CODE 41, CAM SENSOR CIRCUIT - 3.8L
Code 41 will set if engine is running and a cam sensor signal is not received by ECM for last 5 seconds.
NOTE: Test numbers refer to numbers on diagnostic chart.
- Verifies proper operation of circuits No. 633, 644 and 645.
- Tests circuit No. 630 from C(3)I module to ECM.
- If camshaft gear magnet is interfacing with cam sensor, voltage reading will be zero. Bumping engine should correct this condition.
- If voltage reading is constantly varying around a midpoint of 4.6 volts and connections are good, PCM is faulty.
Chevrolet Lumina APV 1993 - Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside insulation. Check for following:
- Poor Connection - Inspect ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection and damaged harness.
- Intermittents - If connections and harness are okay, connect a digital volt-ohmmeter (10-megohm) between ECM CAM signal circuit terminal and ground. Monitor DVOM while moving related connectors and wiring harness. Voltage reading will change if failure is induced. This may help isolate malfunction.
Chevrolet Lumina APV 1993 - CODE 42, ELECTRONIC SPARK TIMING (EXCEPT 3.8L)
Code 42 indicates ECM has seen an open or short to ground in High Energy Ignition Electronic Spark Timing (HEI EST) system or by-pass circuits.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- This test confirms Code 42 and determines if fault is a hard failure or intermittent condition.
- This tests for a normal EST ground path through ignition module. If circuit No. 423 is shorted to ground, reading will be less than 500 ohms.
- As test light voltage touches circuit No. 424, module should switch. This causes ohmmeter to "over-range" with meter in 100-200 ohm range. A higher ohm range will indicate over 5000 ohms. This test assures module switched.
- If module did not switch, this step tests for a short in circuit No. 423, an open in circuit No. 424 and a faulty ignition module connection or module.
- This step confirms Code 42 is a faulty ECM and not an intermittent problem in circuits No. 423 and 424.
Chevrolet Lumina APV 1993 - Diagnostic Aids
The scan tester cannot help diagnose a Code 42 problem. See INTERMITTENTS in TESTS W/O CODES article in this section.
Chevrolet Lumina APV 1993 - CODE 42, ELECTRONIC SPARK TIMING - 3.8L
Code 42 will set if EST or by-pass circuit is open or grounded at time of engine start-up.
NOTE: Test numbers refer to numbers on diagnostic chart.
- Tests if ECM recognizes a problem. If ECM does not set Code 42 at this point, problem is intermittent. Check for a loose connection.
- With ECM disconnected, digital volt-ohmmeter should indicate less than 200 ohms. This is normal EST circuit resistance through ignition module. A higher resistance would indicate a fault in circuit No. 423, a poor ignition module connection or a faulty ignition module.
- If test light was on when connected from 12 volts to ECM harness by-pass circuit, either circuit No. 424 is shorted to ground or ignition module is faulty.
- Tests if ignition module switches when by-pass circuit is energized by 12 volts through test light. If ignition module switches, resistance reading should switch from less than 200 ohms to more than 6000 ohms.
- Disconnecting ignition module should make ohmmeter indicate as if it were monitoring an open circuit (infinite reading). Otherwise, circuit No. 423 is shorted to ground.
Chevrolet Lumina APV 1993 - Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside insulation. Inspect ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection and damaged harness.
If connections and harness are okay, connect a digital volt-ohmmeter between affected terminal to ground, and monitor meter while moving related connectors and wiring harness. If failure is induced, voltage reading will change.
Chevrolet Lumina APV 1993 - CODE 43, ELECTRONIC SPARK CONTROL WITH SPARK CONTROL MODULE
NOTE: Test numbers refer to test numbers on diagnostic chart.
- If conditions for a Code 43 exist, scan tester will display YES. A knock signal should exist at idle unless an internal or system problem exists.
- Determines if system is functioning. Usually, a knock signal can be made by tapping on exhaust manifold. If knock signal is not made, try tapping on engine block near sensor. On models with automatic transmission, it may be necessary to place gear selector lever in Drive.
- Because Code 43 sets when signal voltage on spark retard line remains low, this test should cause signal on that line to go high. The 12-volt signal should be seen by ECM as a "no knock" signal if ECM and wiring are okay.
- This test determines if knock signal is detected on sensor-to-controller line or if ESC module is at fault.
- If sensor line is routed too close to secondary ignition wires, ESC module may see interference as a knock signal.
- This checks ground circuit to module. An open ground will cause voltage on monitored line to remain constant at about 12 volts. This would cause Code 43 functional test to fail.
- This should generate a knock signal to controller. This determines if ESC controller is operating correctly.
Chevrolet Lumina APV 1993 CODE 43 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color 3.8L Knock Signal BB8 Dark Blue 4.3L Turbo Knock Signal GF9 Dark Blue All With 4L60-E Transmission Knock Signal B15 Dark Blue All With 4L80-E Transmission Knock Signal D5 Dark Blue
Chevrolet Lumina APV 1993 CODE 43 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color 4.3L "L/M" Series CPI & 4.3L Knock Signal B15 Dark Blue "S/T" Series Utility Vehicle With M/T Knock Signal B15 Dark Blue 4.3L "S/T" Series Pickup With M/T Knock Signal C12 Dark Blue
Chevrolet Lumina APV 1993 - Diagnostic Aids
Code 43 can be caused by a faulty knock sensor connection at ESC module or ECM. Also, check controller-to-ECM signal line for an open or short to ground.
Chevrolet Lumina APV 1993 - CODE 43, ELECTRONIC SPARK CONTROL WITHOUT ESC MODULE (SINGLE SENSOR) - EXCEPT 4.3L "S" & "T" SERIES PICKUP WITH M/T & 4.3L CPI
NOTE: Test numbers refer to test numbers on diagnostic chart.
- Code 43 will set when vehicle reaches normal operating temperature (but not overheating), high engine load is indicated by MAP sensor and voltage on circuit No. 496 is greater than 3.5 volts DC or less than 1.5 volts DC. This step determines if system is functioning properly at current time.
- This step determines state of 5-volt reference signal applied to sensor.
- Checks knock sensor internal resistance.
Chevrolet Lumina APV 1993 - Diagnostic Aids
ECM/PCM applies and monitors a 5-volt DC signal to knock sensor. Internal knock sensor circuitry pulls this DC signal down to about 2.5 volts. When knock sensor detects detonation, it generates an AC signal which rides back on DC signal to ECM/PCM. Knock signal intensity is dependent upon knock signal level.
Chevrolet Lumina APV 1993 - CODE 43, ELECTRONIC SPARK CONTROL 4.3L "S" & "T" SERIES WITH M/T & "L" & "M" SERIES WITH 4.3L CPI
NOTE: Test numbers refer to test numbers on diagnostic chart.
- Tests to determine if system is currently functioning properly.
- An improperly installed sensor can prevent knock sensor from grounding to block.
Chevrolet Lumina APV 1993 - Diagnostic Aids
VCM applies and monitors a 5-volt DC signal to knock sensors. Internal knock sensor circuitry pulls this DC signal down to about 2.5 volts. When knock sensor detects detonation, it generates an AC signal which rides back on DC signal to VCM. Knock signal intensity is dependent upon knock signal level.
Chevrolet Lumina APV 1993 - CODE 44, LEAN EXHAUST INDICATION (EXCEPT 4.3L TURBO)
Sensor acts like an open sensor circuit and produces no voltage when exhaust temperature is less than 600?F (316?C). An open sensor circuit or cold sensor causes "open loop" operation.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- Code 44 sets when O2 sensor signal remains low for a precalibrated period and system is operating in "closed loop".
Chevrolet Lumina APV 1993 - Diagnostic Aids
Using scan tester, observe Block Learn Memory (BLM) value at different RPMs. If Code 44 conditions exist, block learn value will be around 150-172.
Chevrolet Lumina APV 1993 - O2 Sensor Wire
Wire may be mispositioned and touching exhaust manifold. Check for ground between sensor and wire connector.
Chevrolet Lumina APV 1993 - Fuel Contamination
Water, even small amounts, near in-tank fuel pump inlet can reach fuel injector, causing a lean exhaust and setting Code 44.
Chevrolet Lumina APV 1993 - Fuel Pressure
System will be lean if fuel pressure is low. It may be necessary to monitor fuel pressure while driving vehicle. For fuel pressure checking procedure, see BASIC TESTING article in this section.
Chevrolet Lumina APV 1993 - Exhaust Leaks
If exhaust system has large leaks, exhaust system negative pressure pulses can cause outside air to be drawn into system and past O2 sensor. Vacuum or crankcase leaks can also cause a lean condition. If Code 44 is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.
Chevrolet Lumina APV 1993 CODE 44 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color All With 4L80-E A/T (1) Oxygen Sensor Signal C14 Purple Oxygen Sensor Ground C13 Tan 2.5L, 2.8L, 3.1L & "C", "K" & "P" Series 4.3L (1) & V8 All With Man. Trans. Oxygen Sensor Signal D7 Purple Oxygen Sensor Ground D6 Tan 3.8L Oxygen Sensor Signal BD3 Purple Oxygen Sensor Ground BD2 Tan 4.3L (1) "S" & "T" Series Pickup With Man. Trans. Oxygen Sensor Signal A9 Purple Oxygen Sensor Ground A7 Tan 4.3L "S/T" Series Utility Vehicles W/T & All Models W/ 4L60-E A/T (1) Oxygen Sensor Signal A10 Purple Oxygen Sensor Ground A12 Tan
(1) The 4.3L oxygen sensor has 3 wires: sensor signal, common ground and heating element.
Chevrolet Lumina APV 1993 - CODE 44, LEAN EXHAUST INDICATION - 4.3L TURBO
Sensor acts like an open sensor circuit and produces no voltage when exhaust temperature is less than 600?F (316?C). An open sensor circuit or cold sensor causes "open loop" operation.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- This tests oxygen sensor heating element. Heating element resistance should be 3.5 ohms at 68?F (20?C) and 14 ohms at 562?F (350?C).
- Code 44 sets when O2 sensor signal at ECM is less than .2 volt for at least 2 minutes and system is operating in "closed loop".
Chevrolet Lumina APV 1993 - Diagnostic Aids
Using scan tester, observe Block Learn Memory (BLM) value at different RPMs. If Code 44 conditions exist, block learn value will be around 150.
Chevrolet Lumina APV 1993 - O2 Sensor Wire
Wire may be mispositioned and touching exhaust manifold. Check for ground between sensor and wire connector.
Chevrolet Lumina APV 1993 - Fuel Contamination
Water, even small amounts, near in-tank fuel pump inlet can reach fuel injector, causing a lean exhaust and setting Code 44.
Chevrolet Lumina APV 1993 - Fuel Pressure
System will be lean if fuel pressure is low. It may be necessary to monitor fuel pressure while driving vehicle. For fuel pressure checking procedure, see BASIC TESTING article in this section.
Chevrolet Lumina APV 1993 - Exhaust Leaks
If exhaust system has large leaks, exhaust system negative pressure pulses can cause outside air to be drawn into system and past O2 sensor. Vacuum or crankcase leaks can also cause a lean condition. If Code 44 is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.
Chevrolet Lumina APV 1993 - CODE 45, RICH EXHAUST INDICATION (EXCEPT 4.3L TURBO)
Sensor acts like an open sensor circuit and produces no voltage when exhaust temperature is less than 600?F (316?C). An open sensor circuit or cold sensor causes "open loop" operation. Code 45 indicates a rich exhaust and diagnosis should begin with: fuel pressure, leaking injector, HEI shielding, canister purge saturation, coolant sensor, MAP sensor, O2 sensor contamination and TPS intermittent output.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- Tests if O2 sensor is registering a rich condition. Code 45 is set when vehicle is at operating temperature (in "closed loop"), throttle angle is greater than 5 percent, O2 sensor signal at ECM is greater than .75 volt for 60 seconds or more.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Code 45, rich exhaust, is most likely caused by one of the following:
Chevrolet Lumina APV 1993 - Fuel Pressure High
If fuel pressure is too high, air/fuel ratio will be rich. For fuel pressure checking procedure, see BASIC TESTING article in this section. The ECM can compensate for slight increases but if air/fuel ratio becomes too rich a Code 45 will be set.
Chevrolet Lumina APV 1993 - Ignition Ground
If an open occurs at circuit No. 453, HEI induced electrical "noise" may result, causing simulated reference pulses picked up by ECM on EST harness reference line. Additional pulses result in a higher than actual engine speed signal. The ECM will increase injector pulse width ("on" time) to match increased RPM signal. Scan tester will show higher than actual RPM, which can help diagnose problem.
Chevrolet Lumina APV 1993 - Fuel Canister
Charcoal canister fuel saturation will cause a rich air/fuel ratio. If full of fuel, check canister control and hoses.
Chevrolet Lumina APV 1993 - MAP Sensor
If ECM senses higher than normal manifold pressure (low vacuum) system can go rich. Disconnecting MAP sensor allows ECM to substitute a fixed value for the MAP sensor. If rich condition disappears, replace MAP sensor and continue testing.
Chevrolet Lumina APV 1993 - TPS
An intermittent TPS output will cause system to operate rich due to a false indication of engine acceleration.
Chevrolet Lumina APV 1993 - O2 Sensor Contamination
O2 sensor contamination, caused by silicone in certain fuels or use of improper RTV sealant, may cause a White-powdery coating to cover O2 sensor. The false high signal voltage produced (or low oxygen content sensed) is interpreted by ECM as a rich mixture, causing ECM to set Code 45.
Chevrolet Lumina APV 1993 - EGR Problem
EGR valve sticking open at idle is usually accompanied by a rough idle and/or stalling. If Code 45 is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.
Chevrolet Lumina APV 1993 CODE 45 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION
Application ECM Terminal Wire Color All With 4L80-E A/T (1) Oxygen Sensor Signal C14 Purple Oxygen Sensor Ground C13 Tan 2.5L, 2.8L, 3.1L & "C", "K" & "P" Series 4.3L (1) & V8 All With Man. Trans. Oxygen Sensor Signal D7 Purple Oxygen Sensor Ground D6 Tan 3.8L Oxygen Sensor Signal BD3 Purple Oxygen Sensor Ground BD2 Tan 4.3L (1) "S" & "T" Series Pickup With Man. Trans. Oxygen Sensor Signal A9 Purple Oxygen Sensor Ground A7 Tan 4.3L "S/T" Series Utility Vehicles W/T & All Models W/ 4L60-E A/T (1) Oxygen Sensor Signal A10 Purple Oxygen Sensor Ground A12 Tan
(1) The 4.3L oxygen sensor has 3 wires: sensor signal, common ground and heating element.
Chevrolet Lumina APV 1993 - CODE 45, RICH EXHAUST INDICATION - 4.3L TURBO
Sensor acts like an open sensor circuit and produces no voltage when exhaust temperature is less than 600?F (316?C). An open sensor circuit or cold sensor causes "open loop" operation. Code 45 indicates a rich exhaust and diagnosis should begin with: fuel pressure, leaking injector, HEI shielding, canister purge saturation, coolant sensor, MAP sensor, O2 sensor contamination and TPS intermittent output.
NOTE: Test numbers refer to test numbers on diagnostic chart.
- Tests if O2 sensor is registering a rich condition. Code 45 is set when vehicle is at operating temperature (in "closed loop"), throttle angle is greater than 5 percent, O2 sensor signal at ECM is greater than .75 volt for 50 seconds or more.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Code 45, rich exhaust, is most likely caused by one of the following:
Chevrolet Lumina APV 1993 - Fuel Pressure High
If fuel pressure is too high, air/fuel ratio will be rich. For fuel pressure checking procedure, see BASIC TESTING article in this section. The ECM can compensate for slight increases but if air/fuel ratio becomes too rich a Code 45 will be set.
Chevrolet Lumina APV 1993 - Ignition Ground
If an open occurs at circuit No. 453, HEI induced electrical "noise" may result, causing simulated reference pulses picked up by ECM on EST harness reference line. Additional pulses result in a higher than actual engine speed signal. The ECM will increase injector pulse width ("on" time) to match increased RPM signal. Scan tester will show higher than actual RPM, which can help diagnose problem.
Chevrolet Lumina APV 1993 - Fuel Canister
Charcoal canister fuel saturation will cause a rich air/fuel ratio. If full of fuel, check canister control and hoses.
Chevrolet Lumina APV 1993 - MAP Sensor
If ECM senses higher than normal manifold pressure (low vacuum) system can go rich. Disconnecting MAP sensor allows ECM to substitute a fixed value for MAP sensor. If rich condition disappears, replace MAP sensor and continue testing.
Chevrolet Lumina APV 1993 - TPS
An intermittent TPS output will cause system to operate rich due to a false indication of engine acceleration.
Chevrolet Lumina APV 1993 - O2 Sensor Contamination
O2 sensor contamination, caused by silicone in certain fuels or use of improper RTV sealant, may cause a White-powdery coating to cover O2 sensor. The false high signal voltage produced (or low oxygen content sensed) is interpreted by ECM as a rich mixture, causing ECM to set Code 45.
Chevrolet Lumina APV 1993 - EGR Problem
EGR valve sticking open at idle is usually accompanied by a rough idle and/or stalling. If Code 45 is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.
Chevrolet Lumina APV 1993 - CODE 51, FAULTY PROM/MEM-CAL
Ensure all pins are fully inserted in socket. If okay, replace PROM/MEM-CAL, clear memory and recheck. If Code 51 reappears, replace ECM.
Chevrolet Lumina APV 1993 - CODE 52, FAULTY CALPAK
Ensure all pins are fully inserted in socket. If okay, replace CALPAK, clear memory and recheck. If Code 51 reappears, replace ECM.
Chevrolet Lumina APV 1993 - CODE 53, SYSTEM OVERVOLTAGE (EXCEPT 3.8L)
This code indicates a basic charging system problem. Code 53 will set when voltage at ECM terminal is greater than 17.1 volts for 2 seconds. Check and repair charging system.
Chevrolet Lumina APV 1993 - CODE 55, ECM/PCM ERROR
Ensure ECM grounds are good and MEM-CAL is properly latched. If okay, replace ECM/PCM. Clear codes and confirm closed loop operation. Check operation of SERVICE ENGINE SOON light.
Chevrolet Lumina APV 1993 - CODES 53, 54 & 55, EGR FAULT - 3.8L
Codes 53, 54 and 55 are EGR flow test failures. PCM tests medium and large EGR solenoid valves by cycling each of them on momentarily while monitoring engine RPM. When a solenoid is turned on, PCM expects to see a drop in engine RPM. If expected drop is not detected for EGR solenoid No. 1 for 8 out of 12 tests, Code 53 will set. If expected drop is not detected for medium EGR solenoid (EGR No. 2) for 6 out of 8 tests, Code 54 will set. If expected drop is not detected for large EGR solenoid (EGR No. 3) for 3 out of 5 times, Code 55 will set.
PCM runs EGR flow tests when coolant temperature is greater than 183?F (84?C), vehicle is in a coast-down mode (but not in a fuel-cut situation), O2 sensor voltage is greater than .57 volt, transmission is in 1st or 2nd gear, A/C clutch is not engaged, and vehicle speed is greater than 25 MPH. EGR No. 1 engine test speed range is 800-1000 RPM. EGR No. 2 engine test speed range is 825-1025 RPM. EGR No. 3 engine test speed range is 850-1050 RPM.
NOTE: Test numbers refer to numbers on diagnostic chart.
- A noticeable change in engine speed should occur as each solenoid is cycled on at idle.
- If test light glows, PCM and wiring are okay.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Check for poor harness connections or harness damage. If no problems are found, turn ignition on. Backprobe applicable PCM terminals with a DVOM while wiggling harness. If a failure is induced, voltage reading will change. If no problems are found, check EGR valve pintles and orifices for excessive carbon build-up. Also, check for plugged EGR tube or passages.
Fig. 114: Chevrolet Lumina APV 1993 - Component Locations - CODE 53-55, Schematic, EGR Fault (3.8L)
Fig. 115: Chevrolet Lumina APV 1993 - Component Locations - CODE 53-55, Flowchart, EGR Fault (3.8L)
Chevrolet Lumina APV 1993 - CODE 54, FUEL PUMP CIRCUIT
Code 54 will set if ECM does not see 12 volts on fuel pump signal voltage monitor during the first 2 seconds after ignition is turned on.
Chevrolet Lumina APV 1993 - CODE 56, QUAD-DRIVER "B" FAULT 3.8L
PCM uses Quad-Driver Modules (QDMs) to control several devices. When PCM is commanding a component on, voltage of output circuit will be low (near zero volts). When PCM is commanding component off, voltage of output circuit will be high (near battery voltage). Primary function of quad-driver module is to control ground circuit for component being controlled. PCM has an internal fault line for each quad-driver module. Fault line status can be displayed on a scan tester. If PCM detects an output voltage other than what is expected on fault line, PCM will set Code 56.
NOTE: Test numbers refer to numbers on diagnostic chart.
- PCM does not know which controlled circuit caused Code 56 to set. This chart will check each circuit to determine which is at fault. If other QDM-related codes are present, use those charts first.
- If QDM "B" related symptoms are present, checks on Code 56 chart should isolate cause of fault.
- These steps help determine which circuit is out of specification.
- This step helps determine if problem is circuit or component.
Chevrolet Lumina APV 1993 - QUAD-DRIVER RELATED SYMPTOMS
- Improper shifting.
- TCC will not apply or harsh engagement.
- Poor driveability due to constant EGR.
Chevrolet Lumina APV 1993 - Diagnostic Aids
Monitor voltage at each terminal shown in schematic while moving related harness connectors, including PCM harness. If failure is induced, voltage will change. This may help to isolate an intermittent condition. Check for bent pins at PCM. If code reoccurs with no apparent connection problem, replace PCM.
Chevrolet Lumina APV 1993 - CODE 61, CRUISE VENT SOLENOID - 3.8L
Cruise switch within turn signal lever receives ignition voltage from a 15-amp fuse on circuit No. 639. Cruise switches are inputs to cruise control portion of PCM. Cruise servo and vent and vacuum solenoids are output lines and are controlled by high side drivers in PCM. With ignition on, PCM looks at these output lines and will set a code depending upon actual status of these lines compared with commanded status. In this manner, PCM can detect opens or shorts to ground or voltage. Code 61 does not turn on SERVICE ENGINE SOON light.
Chevrolet Lumina APV 1993 - CODE 62, CRUISE VACUUM SOLENOID - 3.8L
Cruise switch within turn signal lever receives ignition voltage from a 15-amp fuse on circuit No. 639. Cruise switches are inputs to cruise control portion of PCM. Cruise servo, vent and vacuum solenoids are output lines and are controlled by high side drivers in PCM. With ignition on, PCM looks at these output lines and will set a code depending upon actual status of these lines compared with commanded status. In this manner, PCM can detect opens or shorts to ground or voltage. Code 62 does not turn on SERVICE ENGINE SOON light.
Chevrolet Lumina APV 1993 - CODE 63, CRUISE SYSTEM PROBLEM - 3.8L
PCM monitors cruise control system servo position to ensure desired cruise position and actual cruise position are equal to each other. If servo position is low when maximum servo position is commanded, PCM will set Code 63. Code 63 does not turn on SERVICE ENGINE SOON light. If Code 61, 62 or 65 is set with Code 63, repair other code before using this flow chart.
Chevrolet Lumina APV 1993 - CODE 65, CRUISE SERVO POSITION - 3.8L
PCM supplies 5 volts to cruise control servo position sensor. Depending upon actual servo position, voltage on servo position sensor circuit will indicate to PCM position of servo. Code 65 will set if circuit No. 399 is open or if circuit No. 398 is open or shorted to ground or voltage. Code 65 does not turn on SERVICE ENGINE SOON light.
Chevrolet Lumina APV 1993 - CODE 66, LOW A/C REFRIGERANT CHARGE - 3.8L
PCM monitors A/C request and completes ground for A/C relay when an A/C mode is selected at control head and refrigerant pressure is sufficient to close pressure cycling switch. If A/C pressure is low and clutch cycles too often, PCM will protect compressor by disabling A/C relay and setting Code 66. Relay will be disabled until next ignition cycle. If Code 66 is set during 3 consecutive ignition cycles, A/C relay will be disabled until Code 66 is cleared from memory. Code 66 does not illuminate SERVICE ENGINE SOON light. Code 66 will set if A/C request signal lasts less than 1.5 seconds for 10 or more consecutive compressor "on" cycles within a 15 minute period.
Chevrolet Lumina APV 1993 - CODE 67, CRUISE ENGAGE SWITCHES - 3.8L
Code 67 will set if circuit No. 397 or 86 is open, set/coast or resume/accel switch is closed for an extended amount of time or any cruise engage switch circuit is shorted to voltage. Code 67 does not illuminate SERVICE ENGINE SOON light.
Chevrolet Lumina APV 1993 - CODE 68, CRUISE SYSTEM PROBLEM USING TECH 1 - 3.8L
PCM-integrated cruise control system is designed to monitor itself to ensure desired cruise position and actual cruise position are equal to each other. Code 68 sets when actual servo position sensor signal is 15 percent greater than desired servo position sensor signal for .6 second. Code 68 does not illuminate SERVICE ENGINE SOON light. If Code 68 is current, vehicle will operate in "power management" mode. During this mode, PCM will shut of fuel to 3 cylinders to avoid over-revving engine in case of throttle being held open by cruise system malfunction. Power management mode may be perceived as a severe engine miss of lack of power.
NOTE: Test number refers to number on diagnostic chart.
- Most VAC solenoids leak a small amount of vacuum when closed. However, they should not leak enough to allow WOT in 15 seconds with vent closed.
- When VAC solenoid is forced on, vacuum will be vented to atmosphere unless vent valve is stuck closed.
Chevrolet Lumina APV 1993 - Diagnostic Aids
An intermittently binding or sticking throttle cable cam cause a Code 68 to set. Code can also be set by manually compressing servo to increase engine RPM. Outside interference such as CB antenna lead near PCM wiring harness may cause false servo position sensor signal and set Code 68.
Chevrolet Lumina APV 1993 - CODE 69, A/C HEAD PRESSURE SWITCH - 3.8L
A/C head pressure switch opens ground at 210 psi (14.77 kg/cm2 ). When switch is open, fans should run at high speed. If Code 69 is set, engine cooling fans will run at high speed anytime A/C is requested.
