Isuzu Trooper S 1996 - 1996 ENGINE PERFORMANCE Self-Diagnostics - Trooper - 3.2L V6

Isuzu Trooper S 1996 - INTRODUCTION

NOTE:

The CHECK ENGINE light is now referred to as Malfunction Indicator Light (MIL). The MIL is displayed in instrument cluster as CHECK ENGINE.

If no faults were found while performing steps in BASIC TESTING article, proceed with self-diagnostics. If no Diagnostic Trouble Codes (DTCs) are present after entering self-diagnostics, proceed to TESTS W/O CODES article for diagnosis by symptoms.

Isuzu Trooper S 1996 - SYSTEM DESCRIPTION

The PCM monitors engine operation. It also contains a self-diagnostic system which stores Diagnostic Trouble Codes (DTCs) and compares them to On-Board Diagnostics Generation II (OBD-II) standards. Federal law mandates this type of diagnostic system for all vehicles by 1996.

The goal of OBD-II regulation is to provide vehicle with an on-board diagnostic system which is capable of continuously monitoring the efficiency of emission control systems, and to improve diagnosis and repair when system failures occur.

The Federal Test Procedure (FTP) sets maximum allowable emission standards. A Malfunction Indicator Light (MIL) must illuminate if a system or component either fails or deteriorates to a point where the vehicles emissions could rise above 1 1/2 times FTP standards.

DTCs may only be retrieved using an On-Board Diagnostic (OBD-II) scan tester.

Isuzu Trooper S 1996 - TRIP DETECTION LOGIC

Generation II data streams are prioritized. When two messages attempt to establish communications on a data line at the same time, only the message with higher priority will continue. A new segment of the software called the Diagnostic Executive coordinates the protocol for recording and displaying diagnostic procedures.

After engine has reached normal operating temperature, Diagnostic Executive checks if On Board Diagnostic Tests have been completed since last ignition cycle. It checks if tests have passed during current ignition cycle. Checks if fault identified by diagnostic tests is currently active. It also checks if fault identified has been active during current ignition cycle and what operating conditions were present at the time of failure.

Each test is separated in to four types:

Type A - Turns the MIL on the first time an emission related failure occurs. The MIL will FLASH at a rate of once per second to alert the operator of potentially damaging levels of misfire, such that could destroy the catalytic converter.
Type B - Will only turn MIL on if an emission related condition occurs during two consecutive driving cycles. Conditions such as incorrect fuel trim will be stored in the Freez-Frame data until the fault is detected a second time. If the fault is not detected during three consecutive driving cycles, the MIL light will be turned off.
Type C - This is a non-emission related type and will not activate the MIL. It will turn ON a Check Transmission service light, or other non MIL service reminder light.
Type D - Is non-emission related, will not turn the MIL or service light, but will store DTCs of faults present.

Isuzu Trooper S 1996 - SELF-DIAGNOSTIC SYSTEM HARD FAILURES

Hard failures cause Malfunction Indicator Light (MIL) to glow and remain on until problem is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. See DIAGNOSTIC TROUBLE CODE DEFINITIONS. If a sensor fails, Powertrain Control Module (PCM) will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, vehicle runs but driveability will not be optimum.

Isuzu Trooper S 1996 - INTERMITTENT FAILURES

Intermittent failures may cause MIL to flicker or glow and go out after intermittent fault goes away. However, corresponding trouble code will be retained in PCM memory. If related fault does not reoccur within a certain time frame, related trouble code will be erased from PCM memory. Intermittent failures may be caused by a sensor, connector or wiring related problems. See INTERMITTENTS in TESTS W/O CODES article.

Isuzu Trooper S 1996 - FREEZE-FRAME DATA

According to the 1996 government regulations, engine operating conditions under which the MIL is illuminated must be recorded. This record, called freeze frame data, is a snap shot of the driving conditions, that is recorded on the PCM freeze frame buffer and is constantly updated with the most current information.

Freeze frame data can only be overwritten with misfire or fuel trim malfunction data. The data can only be erased by clearing associated history DTCs.

Isuzu Trooper S 1996 - DATA LINK CONNECTOR LOCATION

Located at lower left side of instrument panel, behind a small cover.

Isuzu Trooper S 1996 - RETRIEVING CODES

NOTE:

Codes can be retrieved using a scan tester. Trouble codes are referred to as DTCs.

Code retrieval starts with diagnostic circuit check. See DIAGNOSTIC CIRCUIT CHECK. MIL will come on when ignition is on and engine is not running. When engine is started, MIL should go off. If light remains on while engine is running, a trouble code is present.
If light does not come on with ignition on and engine off, inspect MIL circuit before continuing. If MIL fails to operate, see DIAGNOSTIC CIRCUIT CHECK.
To retrieve codes, install scan tool. Select MIL dash lamp control and command the MIL OFF. Ensure MIL light is off and attempt to start engine. If vehicle does not start, go to vehicle NO-START tests.

Isuzu Trooper S 1996 - CLEARING CODES

After repairs are performed, clear PCM memory of all stored codes. Ensure ignition is off. To clear codes, use diagnostic scan tool "clear DTCs" or "clear info" function. Follow instructions supplied by tool manufacturer, when clearing DTCs.
Trouble codes can also be cleared by disconnecting any PCM power source or negative battery cable for at least 30 seconds. However, if disconnecting battery remember that other memory functions (clock, radio, etc.) will need to be reset.

Isuzu Trooper S 1996 - PCM REPROGRAM PROCEDURE

If PCM requires replacement PCM must be reprogrammed using a Tech I or other OBD II compatible scan tool.

Isuzu Trooper S 1996 - PCM LOCATION

PCM is located near left kick panel.

NOTE:

If any DTCs not listed here are displayed by a scan tool, the scan tool data may be faulty. Notify the scan tool manufacturer of any DTCs displayed that are not included in the DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION table. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION table.

Isuzu Trooper S 1996 - ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK

The On-Board Diagnostic II (OBD-II) System Check is the starting point for any driveability complaint diagnosis. Before any DTC(s) are retrieved, perform a visual underhood inspection checking battery and grounds for clean and tight connections. Check for poor connections or damage to wiring harness and electrical connectors. Check for corroded terminals or corrosion build-up on any connection. Repair as necessary. The OBD-II system check is an organized approach to identifying problems created by an electronic engine control system malfunction.

Use of Tech 2 scan tool is required to perform ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK. To reprogram EEPROM or to program PCM after it has been replaced, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION section.

NOTE:

To identify component terminals and wire colors, see appropriate wiring diagram in WIRING DIAGRAMS article.

NOTE:

Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm impedance, unless stated otherwise in test procedure.

Turn ignition on with engine off. Verify Malfunction Indicator Light (MIL) is on. If MIL is on, go to next step. If MIL is not on, go to BASIC TESTING article.
Turn ignition off. Install Tech 2 scan tool. Turn ignition on. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, verify scan tool is properly installed. If scan tool is properly installed, go to step 8 .
Using scan tool, command MIL OFF. If MIL turns off, go to next step. If MIL does not turn off, go to BASIC TESTING article.
Start engine. If engine starts and continues to run, go to next step. If engine will not run, go to BASIC TESTING article.
Using scan tool, check if any DTCs have been set. If any DTCs are set, go to next step. If no DTCs are set, go to step 7 .
Are 2 or more of the following DTC(s) stored?
- P0107
- P0108
- P0113
- P0118
- P0122
- P0123
- P0712
- P1392
- P1406
If 2 or more of these codes are stored, go to BASIC TESTING article. If a single DTC is stored, go to appropriate DTC test under DIAGNOSTIC TESTS in appropriate TESTS W/CODES article.
Compare PCM data values displayed to typical engine scan data values. See appropriate SCAN TOOL DATA VALUES table under PIN VOLTAGE (VALUE) TESTS in PIN VOLTAGE CHART S article. If values displayed are normal or close to typical values, OBD-II system check is complete. If driveability problem still exists, go to TESTS W/O CODES article. If values are not correct, go to I - SYSTEM & COMPONENT TESTS article.
Turn ignition off. Disconnect PCM connectors. Turn ignition on with engine off. Check for open or short in class 2 data circuit (Orange/Green wire) between Data Link Connector (DLC) terminal No. 2 and PCM 32-pin connector C-1, terminal B13. Also check for open or short in ignition feed circuit (Green/White wire) between DLC terminal No. 16 and dash fuse box. Also check for open in ground circuit (Black wire) to DLC terminal No. 4. If problem is found, repair as necessary and return to step 2 . If no problem is found, go to next step.
Attempt to reprogram EEPROM. Programming PCM/EEPROM requires the use of a scan tool and special manufacturer equipment. Attempt to display PCM data on scan tool. If data is now displayed, return to step 2 . If data is not displayed, go to next step.
Replace PCM. Program PCM. After repair, return to step 2 .

Isuzu Trooper S 1996 - DIAGNOSTIC TROUBLE CODE DEFINITIONS

Isuzu Trooper S 1996 DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION

DTC

Type⁽¹⁾

Component/System

Most Likely Cause

P0101

MAF Sensor Ckt Range/Performance Problem

MAF Sensor

P0102

MAF Sensor Ckt Low Frequency

Open/Short, MAF Sensor Or PCM

P0103

MAF Sensor Ckt High Frequency

Open/Short, MAF Sensor Or PCM

P0106

MAP Sensor Ckt Range/Performance Problem

MAP Sensor

P0107

MAP Sensor Ckt Low Frequency

Open/Short, MAP Sensor Or PCM

P0108

MAP Sensor Ckt High Frequency

Open, MAP Sensor Or PCM

P0112

IAT Sensor Ckt Low Frequency

Short, IAT Sensor Or PCM

P0113

IAT Sensor Ckt High Frequency

Open, IAT Sensor Or PCM

P0117

ECT Sensor Ckt Low Frequency

Short, ECT Sensor Or PCM

P0118

ECT Sensor Ckt High Frequency

Open, ECT Sensor Or PCM

P0121

TP Sensor Ckt Range/Performance Problem

TP Sensor Or PCM

P0122

TP Sensor Ckt Low Frequency

Open/Short, TP Sensor Or PCM

P0123

TP Sensor Ckt High Frequency

Open Ckt, TP Sensor Or PCM

P0125

ECT Sensor Ckt Excessive Warm-Up Time To Closed Loop

Cooling System, ECT Or PCM

P0131

Bank 1 Primary HO2S Ckt Low Voltage

Short, HO2S Sensor, Fuel Supply Or PCM

P0132

Bank 1 Primary HO2S Ckt High Voltage

Open, HO2S Sensor Or PCM

P0133

Bank 1 Primary HO2S Slow Response

HO2S Sensor Or Exhaust System

P0134

Bank 1 Primary HO2S Insufficient Activity

Poor Connections, HO2S Sensor Or PCM

P0135

Bank 1 Primary HO2S Heater Ckt Malfunction

Open/Short Or PCM

P0137

Bank 1 Secondary HO2S Ckt Low Voltage

Short, HO2S Or PCM

P0138

Bank 1 Secondary HO2S Ckt High Voltage

Open, HO2S Or PCM

P0140

Bank 1 Secondary HO2S Ckt. Insufficient Activity

Short In Ckt, HO2S Or PCM

P0141

Bank 1 Secondary HO2S Ckt Malfunction

Open/Short In Heater Ckt Or PCM

P0143

Bank 1 Secondary HO2S Low Voltage (M/T Only)

Short, HO2S Or PCM

P0144

Bank 1 Secondary HO2S High Voltage (M/T Only)

Open/Short, HO2S Or PCM

P0146

Bank 1 Secondary HO2S Insufficient Activity (M/T Only)

Short, HO2S Or PCM

P0147

Bank 1 Secondary HO2S Heater Ckt (M/T Only)

Short Or HO2S

P0151

Bank 2 Secondary HO2S Ckt Low Voltage

Short Or PCM

P0152

Bank 2 Secondary HO2S Ckt High Voltage

Short, HO2S Or PCM

P0153

Bank 2 Secondary HO2S Ckt Slow Response

Open/Short, HO2S Contamination Or PCM

P0154

Bank 2 Secondary HO2S Insufficient Activity

HO2S Or PCM

P0155

Bank 2 Secondary HO2S Heater Ckt

Short Or HO2S

P0157

Bank 2 Secondary HO2S Ckt Low Voltage (A/T Only)

Short Or PCM

P0158

Bank 2 Secondary HO2S Ckt. High Voltage (A/T Only)

Short, HO2S Or PCM

P0160

Bank 2 Secondary HO2S Ckt Insufficient Activity (A/T Only)

Short, HO2S Or PCM

P0161

Bank 2 Secondary HO2S Heater Ckt LOAD Malfunction (A/T Only)

Short Or HO2S

P0171

Bank 1 System Too Lean

Fuel Supply/Contamination, Primary HO2S, MAP, Leaking Exhaust Or Valve Clearance

P0172

Bank 1 System Too Rich

Fuel Supply, Primary HO2S, MAP Sensor, Fuel Contamination Or Valve Clearance

P0174

Bank 2 System Too Lean

Air Intake System, MAF Sensor, Fuel Supply Or Exhaust System

P0175

Bank 2 System Too Rich

Air Intake System, MAF Sensor, Fuel Supply Or TP Sensor

P0201

Injector No. 1 Ckt Malfunction

Open/Short Or PCM

P0202

Injector No. 2 Ckt Malfunction

Open/Short Or PCM

P0203

Injector No. 3 Ckt Malfunction

Open/Short Or PCM

P0204

Injector No. 4 Ckt Malfunction

Open/Short Or PCM

P0205

Injector No. 5 Ckt Malfunction

Open/Short Or PCM

P0206

Injector No. 6 Ckt Malfunction

Open/Short Or PCM

P0218⁽²⁾

Transmission High Temperature Condition (A/T Only)

Miscellaneous

P0300

Random Misfire Detected

Ignition System, Fuel Supply, MAP Sensor, EGR System, IAC Valve Or Contaminated Fuel

P0301

Cylinder No. 1 Misfire Detected

Miscellaneous

P0302

Cylinder No. 2 Misfire Detected

Miscellaneous

P0303

Cylinder No. 3 Misfire Detected

Miscellaneous

P0304

Cylinder No. 4 Misfire Detected

Miscellaneous

P0305

Cylinder No. 5 Misfire Detected

Miscellaneous

P0306

Cylinder No. 6 Misfire Detected

Miscellaneous

P0325

Knock Sensor (KS) Ckt Malfunction

PCM

P0327

Knock Sensor (KS) Ckt

Open/Short, KS Or PCM

P0336

CKP Sensor Range/Performance

CKP Sensor, Valve Timing Or Timing Belt Skipped Teeth

P0337

CKP Ckt Low Frequency

Open/Short, CKP Sensor Or PCM

P0341

CKP Ckt Performance

Open/Short, CKP Sensor, Faulty Or Missing CKP Magnet OR PCM Missing CKP Magnet Or PCM

P0342

CKP Sensor Low Frequency

CKP Sensor/Magnet Or PCM

P0351

Ignition Coil 1 Ckt

Ignition Control Module (ICM), Open/Short Or PCM Miscellaneous

P0352

Ignition Coil 2 Ckt

Miscellaneous

P0353

Ignition Coil 3 Ckt

Miscellaneous

P0354

Ignition Coil 4 Ckt

Miscellaneous

P0355

Ignition Coil 5 Ckt

Miscellaneous

P0356

Ignition Coil 6 Ckt

Miscellaneous

P0401

Insufficient EGR Flow Detected

EGR Valve Or Line

P0420

Bank 1 Catalyst System Efficiency Below Threshold

Catalytic Converter Or Secondary HO2S

P0430

Bank 2 Catalyst System Efficiency Below Threshold (A/T Only)

Catalytic Converter Or Secondary HO2S

P0440

EVAP System

Canister Purge Valve, Vent Solenoid Or Hoses

P0441

⁽³⁾ Evaporative Emission Control System, Incorrect Purge Flow

EVAP Canister, Vacuum Switch, Purge Solenoid Or PCM

P0442

EVAP Small Leak Detected

Vent Solenoid, Fuel Cap Or Lines

P0446

EVAP Canister Vent Blocked

Vent Solenoid Or Canister

P0502

VSS Ckt Low Frequency

Open/Short, VSS Or PCM

P0506

Idle Control System Low RPM

IAC Valve Or PCM

P0507

Idle Control System High RPM

IAC Valve Or PCM

P0560⁽²⁾

System Voltage Malfunction (A/T Only)

Miscellaneous

P0562

System Voltage Low

Open Or PCM

P0563

System Voltage High

PCM

P0601

PCM Memory Check Sum Error

PCM

P0700⁽²⁾

Automatic Transaxle

Miscellaneous

P0705⁽²⁾

Trans. Range Sensor Ckt Malfunction

Miscellaneous

P0706⁽²⁾

Trans. Range Sensor Rationality

Miscellaneous

P0712⁽²⁾

Trans. Fluid Temperature Low Voltage

Miscellaneous

P0713⁽²⁾

Trans. Fluid Temperature High Voltage

Miscellaneous

P0715⁽²⁾

Trans. Jerks Hard When Shifting (A/T)

Open/Short In Mainshaft Speed Sensor Ckt Or Faulty Mainshaft Speed Sensor

P0719⁽²⁾

Brake Switch Ckt Low

Miscellaneous

P0720⁽²⁾

Lock-up Clutch Does Not Engage (A/T)

Open Or Short In Countershaft Speed Sensor Ckt

P0720⁽²⁾

Lock-up Clutch Does Not Engage (A/T)

Or Faulty Countershaft Speed Sensor

P0722⁽²⁾

Output Speed Sensor Ckt No Signal

Miscellaneous

P0723⁽²⁾

Output Speed Sensor Ckt Intermittent Signal

Miscellaneous

P0724⁽²⁾

Brake Switch Ckt High

Miscellaneous

P0730⁽²⁾

Won't Shift Between 1/2nd, 2/3rd, 2/4th. Stuck in 1st Or 4th gears (A/T)

Faulty Shift Control System

P0740⁽²⁾

.....

Lock-up clutch does not engage/disengage Unstable Idle Speed (A/T)

Faulty Lock-up Control system

P0742⁽²⁾

Torque Converter Clutch Ckt Stuck On

Miscellaneous

P0748⁽²⁾

Trans. Pressure Control Solenoid Electrical Ckt Fault

Miscellaneous

P0751⁽²⁾

Trans. Shift Solenoid "A" Performance Or Stuck Off (A/T Only)

Miscellaneous

P0753⁽²⁾

Trans. Shift Solenoid "A" - Electrical Ckt Fault

Open/Short In Ckt. Or Faulty Solenoid

P0756⁽²⁾

Trans. Shift Solenoid "B" Performance Stuck Off (A/T Only)

Miscellaneous

P0758⁽²⁾

Trans. Shift Solenoid "B" - Electrical Ckt Fault

Open/Short In Ckt Or Faulty Solenoid

P1106

MAP Ckt Intermittent High Voltage

Open/Short In Ckt

P1107

MAP/Barometric Pressure Ckt Low Voltage

Intermittent Open/Short Or PCM

P1111

IAT Ckt Intermittent High Voltage

Poor Ground/Open Ckt

P1112

IAT Ckt Intermittent Low Voltage

Short In Ckt

P1114

ECT Ckt Intermittent Low Voltage

Intermittent Short

P1115

ECT Ckt Intermittent High Voltage

Poor PCM Ground Or Open

P1121

TP Ckt Intermittent High Voltage

Open/Short Or Poor Ground In Ckt

P1122

TP Ckt Intermittent Low Voltage

Open/Short Or Poor Ground In Ckt

P1133

Bank 1 Primary HO2S Ckt Insufficient Switching

Exhaust Leak, Short In Ckt, HO2S Or PCM

P1134

Bank 1 Primary HO2S Ckt Transition Time Ratio

Exhaust Leak, Open/Short In Ckt, HO2S Or PCM

P01153

Bank 2 Primary HO2S Ckt Insufficient Switching

Exhaust Leak, Short In Ckt, HO2S Or PCM

P1154

Bank 2 Primary HO2S Ckt Transition Time Ratio

Exhaust Leak, Open/Short In Ckt, HO2S Or PCM

P1171

Fuel System Lean During Acceleration

Fuel Pressure, Incorrect Fuel Or Hot Fuel

P1390

G-Sensor Ckt Intermittent Low Voltage

Open/Short

P1391

G-Sensor Ckt Performance

G-Sensor Or PCM

P1392

G-Sensor Ckt Low Voltage

PCM

P1393

G-Sensor Ckt High Voltage

Poor Grounds, G-Sensor Or PCM

P1394

G-Sensor Ckt Intermittent High Voltage

Poor Ground, MAP Or G-Sensor

P1406

EGR Valve Pintle Position Ckt

Open/Short, EGR Or PCM

P1441

EVAP System Flow During Non-Purge

Short, PCM, EVAP Control Solenoid Or EVAP Vacuum Switch

P1442

EVAP System Vacuum Switch Circuit

Open/Short, PCM Or EVAP Vacuum Switch

P1508

Idle Control System Low RPM

IAC Valve Ckt Or PCM

P1509

Idle Control System High RPM

Vacuum Leaks, IAC Ckt Or PCM

P1618

Serial Peripheral Interface. PCM Interprocessor Communication Error

PCM

P1640

ODM "A" Fault

Open in Ignition Ckt Or PCM

P1705⁽²⁾

.....

⁽³⁾

Short In A/T Gear Position Switch Wire Or Faulty A/T Gear Position Switch

P1706⁽²⁾

.....

⁽⁴⁾

Open A/T Gear Position Switch Ckt Or Faulty A/T Gear Position Switch

P1753⁽²⁾

.....

Lock-Up Clutch Does Not Engage Or Disengage. Unstable Idle (A/T)

Open/Short In Lock-Up Control Solenoid

P1753⁽²⁾

.....

Lock-up Clutch Won't Engage/Disengage. Unstable Idle (A/T)

Valve "A" Ckt Or Faulty Solenoid

P1758⁽²⁾

.....

Lock-up Clutch Does Not Engage (A/T)

Open/Short In Lock-up Control Solenoid

P1758⁽²⁾

.....

Lock-up Clutch Does Not Engage (A/T)

Valve "B" Ckt Or Faulty Solenoid

P1860

TCC PWM Solenoid Ckt Fault

Miscellaneous

P1870

Transmission Component Slipping

Miscellaneous

⁽¹⁾	See TRIP DETECTION LOGIC for type Definitions

⁽²⁾	See appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS section.

⁽³⁾	Only Shifts In 2nd and 4th Gears. Lock-up Clutch Does Not Engage (A/T).

⁽⁴⁾	Only Shifts In 2nd And 4th Gears. Lock-up Clutch Does Not Engage Or Engages and Disengages Alternately (A/T).

Isuzu Trooper S 1996 - CIRCUIT TESTS

NOTE:

See PIN VOLTAGE CHARTS article and WIRING DIAGRAMS section at the end of this article for PCM harness connector, wire terminal and wire color identification.

NOTE:

If PCM requires replacement, PCM must be reprogrammed using a Tech 1 or other OBD-II compatible scan tool.

Isuzu Trooper S 1996 - DTC P0101 - MASS AIRFLOW (MAF) SENSOR CIRCUIT PERFORMANCE

Perform On-Board Diagnostic (OBD) System Check. See BASIC DIAGNOSTIC PROCEDURES article. Go to next step.
Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0101 is not set, check for an intermittent problem. See TESTS W/O CODES article. If DTC P0101 is set, replace MAF sensor. Retest system.

Isuzu Trooper S 1996 - DTC P0102 - MAF SENSOR CIRCUIT/LOW FREQUENCY

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
Start engine and allow it to reach normal operating temperature. With engine at idle, monitor MAF FREQUENCY parameter on scan tool. If display is less than 1000 Hz, go to next step. If display is 1000 Hz or greater, go to step 5).
With ignition on and engine off, review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0102 is set, go to next step. If DTC P0102 is not set, check for an intermittent problem. See TESTS W/O CODES article.
Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on. Using a voltmeter, measure voltage between ground and MAF sensor signal circuit at connector. If reading is 5 volts, go to next step. If reading is not as specified, go to step 8).
Using a test light, check for voltage between sensor ground circuit and voltage supply circuit at MAF sensor harness connector. If test light comes on, go to step 7). If test light does not come on, go to next step.
Using a test light, check for voltage between ground and voltage supply circuit at MAF sensor connector. If test light comes on, go to step 11). If test light does not come on, go to step 12).
Check for poor connection at MAF sensor. Repair as necessary. Retest system. If connections are okay, go to step 13).
Turn ignition off. Disconnect PCM harness connector related to MAF sensor circuit. Turn ignition on. Using a voltmeter, measure voltage between ground and MAF signal terminal at PCM. If reading is less than 4 volts, go to next step. If reading is not as specified, go to step 10).
Turn ignition off. Disconnect White PCM harness connector. Turn ignition on. Using a voltmeter, check MAF sensor signal circuit for short to voltage supply circuit. Repair as necessary. Retest system.
Turn ignition off. Disconnect White PCM harness connector. Using an ohmmeter, check sensor signal circuit between MAF sensor harness connector and PCM for an open, short to ground or short to sensor ground circuit. Repair as necessary. Retest system. If wire is okay, go to step 13).
Locate and repair open in sensor ground circuit between MAF sensor harness connector and PCM. Retest system.
Locate and repair open in voltage supply circuit between MAF sensor harness connector and PCM. Retest system.
Replace MAF sensor. Retest system. If DTC P0102 resets, replace PCM. Retest system.

Isuzu Trooper S 1996 - DTC P0103 - MASS AIRFLOW (MAF) SENSOR CIRCUIT/HIGH FREQUENCY

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0103 is set, go to next step. If DTC P0103 is not set, check for an intermittent problem. See TESTS W/O CODES article.
Start engine and allow it to reach normal operating temperature. With engine at idle, monitor MAF FREQUENCY parameter on scan tool. If display is greater than 9500 Hz, go to next step. If display is 9500 Hz or less, go to step 7).
Turn ignition off. Disconnect MAF sensor harness connector. Start engine and let idle. Using scan tool, monitor MAF FREQUENCY parameter. If display is zero Hz, go to next step. If display is not as specified, go to step 6).
Replace MAF sensor. Retest system. If DTC P0103 resets, replace PCM. If DTC P0103 does not reset, repair is complete.
Check MAF sensor harness for incorrect routing near high voltage components (solenoids, relays or motors). Repair as necessary. If MAF sensor harness is okay, replace PCM. Retest system.
With engine at idle, monitor MAF FREQUENCY parameter on scan tool. Snap throttle wide open and release while observing scan tool display. If display reading was greater than 9500 Hz, go to step 5). If display reading was not as specified, replace PCM. Retest system.

Isuzu Trooper S 1996 - DTC P0106 - MAP SENSOR CIRCUIT PERFORMANCE

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0106 is set, go to step 4). If DTC P0106 is not set, go to next step.
Check for the following conditions:
- MAP sensor seal missing or damaged.
- Vacuum hoses disconnected, damaged or misrouted.
- Intake manifold leaks.
- Vacuum leaks at throttle body or EGR valve and/or piping.
- PCV valve improperly installed, damaged or missing.
Repair as necessary. Retest system. If no problems are found, check for an intermittent problem. See TESTS W/O CODES article.
Turn ignition off. Disconnect MAP sensor harness connector. Turn ignition on. Observe MAP sensor parameter on scan tool. If display is about 10 kPa, go to next step. If display is not as specified, go to step 12).
Connect a test light between battery positive terminal and sensor signal circuit at MAP sensor harness connector. If display on scan tool is about 104 kPa, go to next step. If display is not as specified, go to step 9).
Using a fused jumper wire, connect voltage reference circuit and signal circuit together at MAP sensor harness connector. If display on scan tool is about 104 kPa, go to next step. If display is not as specified, go to step 8).
Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check MAP sensor ground circuit for high resistance, open or poor connection. Repair as necessary. Retest system. If wire is okay, go to step 11).
Turn ignition off. Using an ohmmeter, check MAP sensor voltage reference circuit for high resistance, open or poor connection. Repair as necessary. Retest system. If wire is okay, go to step 10).
Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check MAP sensor signal circuit for high resistance, open or poor connection. Repair as necessary. Retest system. If wire is okay, go to next step.
Check MAP sensor signal circuit for poor connection at PCM. Repair as necessary. If wire is okay, replace PCM. Retest system.
Check for poor connection at MAP sensor. Repair as necessary. If connection is okay, replace MAP sensor. Retest system.
Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using a voltmeter, check MAP sensor signal circuit for a short to battery voltage or voltage reference circuit. Repair as necessary. If wire is okay, replace PCM. Retest system.

Isuzu Trooper S 1996 - DTC P0107 - MAP SENSOR CIRCUIT/LOW VOLTAGE

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
Turn ignition on. With throttle fully closed, observe MAP sensor parameter on scan tool. If display is 10 kPa at sea level, go to step 4). If display is not as specified, go to next step.
Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0107 is set, go to next step. If DTC P0107 is not set, check for an intermittent problem. See TESTS W/O CODES article.
Turn ignition off. Disconnect MAP sensor harness connector. Using a fused jumper wire, connect sensor ground circuit and sensor signal circuit together at MAP sensor harness connector. Turn ignition on. Observe MAP sensor parameter on scan tool. If display is about 5 volts and 104 kPa, replace MAP sensor. Retest system. If display is not as specified, go to next step.
Remove jumper wire. Connect a test light between battery positive terminal and sensor signal circuit at MAP sensor harness connector. If display on scan tool is about 5 volts and 104 kPa, go to next step. If display is not as specified, go to step 8).
Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check voltage reference circuit for an open or short to ground. Repair as necessary. Retest system. If wire is okay, go to next step.
Check voltage reference circuit for poor connection at PCM. Repair as necessary. If connection is okay, replace PCM. Retest system.
Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check MAP sensor signal circuit for an open, short to ground or short to sensor ground circuit. Repair as necessary. Retest system. If wire is okay, go to next step.
Check MAP sensor signal circuit for a poor connection at PCM or MAP sensor. Repair as necessary. If wire is okay, replace PCM. Retest system.

Isuzu Trooper S 1996 - DTC P0108 - MAP SENSOR CIRCUIT/HIGH VOLTAGE

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.

NOTE: If idle is rough or unstable, repair idle problem first. See TESTS W/O CODES article.
Start engine and allow it to reach normal operating temperature. With engine at idle, note MAP sensor value on scan tool. If display is greater than 90 kPa, go to step 4). If reading is not as specified, go to next step.
Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0108 is set, go to next step. If DTC P0108 is not set, check for an intermittent problem. See TESTS W/O CODES article.
Turn ignition off. Disconnect MAP sensor harness connector. Turn ignition on. Note MAP sensor voltage on scan tool. If display is zero volts and 10 kPa, go to next step. If display is not as specified, go to step 6).
Using a test light connected to ground, probe MAP sensor ground circuit. If test light comes on, go to step 7). If test light does not come on, go to step 9).
Using a voltmeter, check MAP sensor signal circuit for a short to battery voltage or voltage reference circuit. Repair as necessary. If wire is okay, replace PCM. Retest system.
Check for poor ground circuit connection at MAP sensor harness connector. Repair as necessary. Retest system. If connection is okay, go to next step.
Check for restricted or leaking vacuum hose to MAP sensor. Repair as necessary. If vacuum supply is okay, replace MAP sensor. Retest system.
Check for poor MAP sensor ground circuit connection at PCM. Repair as necessary. Retest system. If connection is okay, go to next step.
Turn ignition off. Using an ohmmeter, measure resistance between MAP sensor ground circuit at MAP sensor harness connector and chassis ground. If resistance is greater than 5 ohms, repair open or poor connection. If MAP sensor ground is okay, replace PCM. Retest system.

Isuzu Trooper S 1996 - DTC P0112 - IAT CIRCUIT/LOW VOLTAGE

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
Turn ignition on. Using scan tool, monitor IAT sensor parameter. If display is greater than 283?F, go to step 4). If display is not as specified, go to next step.

Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0112 is set, check resistance of IAT sensor at specified temperatures. See INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE table. Replace IAT sensor if it does not test as specified. If DTC P0112 is not set, check for an intermittent problem. See TESTS W/O CODES article.

Isuzu Trooper S 1996 INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE

Temperature ?F (?C)	Ohms
-40 (-40)	100,700
-22 (-30)	52,700
5 (-15)	21,450
23 (-5)	12,300
41 (5)	7280
59 (15)	4450
77 (25)	2796
95 (35)	1802
113 (45)	1188
140 (60)	667
176 (80)	332
212 (100)	177

Turn ignition off. Disconnect IAT sensor harness connector. Turn ignition on. Observe IAT parameter on scan tool. If display is less than -36?F, replace IAT sensor. Retest system. If display is not as specified, go to next step.
Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check IAT sensor signal circuit for short to ground. Repair as necessary. If wire is okay, replace PCM. Retest system.

Isuzu Trooper S 1996 - DTC P0113 - INTAKE AIR TEMPERATURE (IAT) CIRCUIT/HIGH VOLTAGE

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
Turn ignition on. Using scan tool, monitor IAT sensor parameter. If display is less than -36?F, go to step 4). If display is not as specified, go to next step.
Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0113 is set, check resistance of IAT sensor at specified temperatures. See INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE table in DTC P0112. Replace IAT sensor if it does not test as specified. If DTC P0113 is not set, check for an intermittent problem. See TESTS W/O CODES article.
Turn ignition off. Disconnect IAT sensor harness connector. Using a fused jumper wire, connect terminals of IAT sensor harness connector together. Turn ignition on. Observe IAT sensor parameter on scan tool. If display is 284?F, go to step 6). If display is not as specified, go to next step.
Jumper IAT sensor signal circuit to ground. If display on scan tool is 284?F, go to step 7). If display is not as specified, go to step 8).
Check for poor connections at IAT sensor harness connector. Repair as necessary. If connections are okay, replace IAT sensor. Retest system.
Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check IAT sensor ground circuit for an open. Repair as necessary. Retest system. If wire is okay, go to step 9).
Turn ignition off. Disconnect PCM harness connector. Using an ohmmeter, check IAT sensor signal circuit for an open. Repair as necessary. Retest system. If wire is okay, go to next step.
Check for a poor IAT sensor ground circuit or signal circuit connection at PCM. Repair as necessary. If wires are okay, replace PCM. Retest system.

Isuzu Trooper S 1996 - DTC P0117 - ECT CIRCUIT/LOW VOLTAGE

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
Turn ignition on. Using scan tool, monitor ECT sensor parameter. If display is less than 282?F, go to step 4). If display is not as specified, go to next step.

Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0117 is set, check resistance of ECT sensor at specified temperatures. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE table. Replace ECT sensor if it does not test as specified. If DTC P0117 is not set, check for an intermittent problem. See TESTS W/O CODES article.

Isuzu Trooper S 1996 ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE

Temperature ?F (?C)	Ohms
-40 (-40)	100,700
-22 (-30)	52,700
5 (-15)	21,450
23 (-5)	12,300
41 (5)	7280
59 (15)	4450
77 (25)	2796
95 (35)	1802
113 (45)	1188
140 (60)	667
176 (80)	332
212 (100)	177

Turn ignition off. Disconnect ECT sensor harness connector. Turn ignition on. Observe ECT parameter on scan tool. If display is -38?F, replace ECT sensor. Retest system. If display is not as specified, go to next step.
Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check ECT sensor signal circuit for short to sensor ground circuit. Repair as necessary. If wire is okay, replace PCM. Retest system.

Isuzu Trooper S 1996 - DTC P0118 - ECT CIRCUIT/HIGH VOLTAGE

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
Turn ignition on. Using scan tool, monitor ECT sensor parameter. If display is less than -38?F, go to step 4). If display is not as specified, go to next step.
Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0118 is set, check resistance of ECT sensor at specified temperatures. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE table in DTC P0117. Replace ECT sensor if it does not test as specified. If DTC P0118 is not set, check for an intermittent problem. See TESTS W/O CODES article.
Turn ignition off. Disconnect ECT sensor harness connector. Using a fused jumper wire, connect terminals of ECT sensor harness connector together. Turn ignition on. Observe ECT sensor parameter on scan tool. If display is 284?F, go to step 6). If display is not as specified, go to next step.
Jumper ECT sensor signal circuit to ground. If display on scan tool is 284?F, go to step 7). If display is not as specified, go to step 8).
Check for poor connections at ECT sensor harness connector. Repair as necessary. If connections are okay, replace ECT sensor. Retest system.
Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check ECT sensor ground circuit for an open. Repair as necessary. Retest system. If wire is okay, go to step 9).
Turn ignition off. Disconnect PCM harness connector. Using an ohmmeter, check IAT sensor signal circuit for an open. Repair as necessary. Retest system. If wire is okay, go to next step.
Check for a poor IAT sensor ground circuit or signal circuit connection at PCM. Repair as necessary. If wires are okay, replace PCM. Retest system.

Isuzu Trooper S 1996 - DTC P0121 - THROTTLE POSITION (TP) SENSOR CIRCUIT PERFORMANCE

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
Turn ignition on. Observe MAP sensor parameter on scan tool. If display is less than 65 kPa, go to next step. If display is not as specified, go to step 5).
Turn ignition off. Disconnect MAP sensor harness connector. Connect a test light between MAP sensor voltage reference circuit and MAP sensor signal circuit at harness connector. Turn ignition on. If display on scan tool is less than 65 kPa, replace MAP sensor. Retest system. If display is not as specified, go to next step.
Turn ignition off. Using an ohmmeter, check for an open, short to ground or short to MAP sensor ground circuit. Repair as necessary. If wire is okay, replace PCM. Retest system.
Observe TP sensor angle on scan tool while slowly opening throttle. If display shows a steady increase from zero percent to 100 percent, check for an intermittent problem. See TESTS W/O CODES article. If display is not as specified, go to next step.
Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on. Observe TP sensor parameter on scan tool. If display is zero volts, go to next step. If display is not as specified, go to step 8).
Turn ignition off. Connect a test light between voltage reference circuit and sensor signal circuit at TP sensor harness connector. Turn ignition on. If display is 5 volts, replace TP sensor. Retest system. If display is not as specified, go to step 9).
Check for the following items:
- TP sensor signal circuit shorted to power.
- High resistance in TP sensor ground circuit.
Repair as necessary. If no problems are found, replace PCM. Retest system.
Check for the following items:
- Poor connection in TP sensor signal circuit or voltage reference circuit.
- High resistance in TP sensor voltage reference circuit.
  Repair as necessary. If no problems are found, replace PCM. Retest system.

Isuzu Trooper S 1996 - DTC P0122 - THROTTLE POSITION (TP) SENSOR CIRCUIT/LOW VOLTAGE

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
Turn ignition on. With throttle closed, observe TP sensor parameter on scan tool. If display is less than 0.22 volt, go to step 4). If display is not as specified, go to next step.
Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0122 is set, go to next step. If DTC P0122 is not set, check for an intermittent problem. See TESTS W/O CODES article.
Turn ignition off. Disconnect TP sensor harness connector. Using a fused jumper wire, connect voltage reference circuit to sensor signal circuit at harness connector. Turn ignition on. Observe display on scan tool. If display is 5 volts, go to step 10). If display is not as specified, go to next step.
Remove jumper wire. Connect a test light between battery positive terminal and sensor signal circuit at TP sensor harness connector. If display on scan tool is 5 volts, go to next step. If display is not as specified, go to step 8).
Turn ignition off. Disconnect PCM harness connector. Using an ohmmeter, check for an open or short to ground in voltage reference circuit. Repair as necessary. Retest system. If wire is okay, go to next step.
Check voltage reference circuit for poor connection at PCM. Repair as necessary. If connection is okay, replace PCM. Retest system.
Turn ignition off. Disconnect PCM harness connector. Using an ohmmeter, check TP sensor signal circuit for an open, short to ground or short to sensor ground circuit. Repair as necessary. Retest system. If wire is okay, go to next step.
Check TP sensor signal circuit for poor connection at PCM. Repair as necessary. If connection is okay, replace PCM. Retest system.
Check TP sensor signal circuit for poor connection at TP sensor. Repair as necessary. If connection is okay, replace TP sensor. Retest system.

Isuzu Trooper S 1996 - DTC P0123 - THROTTLE POSITION (TP) SENSOR CIRCUIT/LOW VOLTAGE

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
Turn ignition on. With throttle closed, observe TP sensor parameter on scan tool. If display is greater than 4.88 volts, go to step 4). If display is not as specified, go to next step.
Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0123 is set, go to next step. If DTC P0123 is not set, check for an intermittent problem. See TESTS W/O CODES article.
Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on. Observe display on scan tool. If display is about zero volts, go to next step. If display is not as specified, go to step 6).
Using a test light connected to battery positive terminal, probe TP sensor ground circuit at harness connector. If test light comes on, go to step 7). If test light does not come on, go to step 10).
Turn ignition off. Disconnect PCM harness connector. Turn ignition on. Using a voltmeter, check TP sensor signal circuit for a short to power. Repair as necessary. If wire is okay, replace PCM. Retest system.
Turn ignition on. Observe TP sensor parameter on scan tool while disconnecting each sensor which shares same voltage reference circuit. See WIRING DIAGRAMS section. If display changes while disconnecting a sensor, replace that sensor. Repair as necessary. If display does not change, go to next step.
Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using a voltmeter, check voltage reference circuit for short to battery voltage. Repair as necessary. Retest system. If wire is okay, go to next step.
Check for poor connection at TP sensor. Repair as necessary. If connection is okay, replace TP sensor. Retest system.
Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, check for open in TP sensor ground circuit. Repair as necessary. If wire is okay, replace PCM. Retest system.

Isuzu Trooper S 1996 - DTC P0125 - INSUFFICIENT COOLANT TEMPERATURE FOR CLOSED LOOP

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
If any Engine Coolant Temperature (ECT) DTCs are set, see appropriate DTC test. If no DTCs are set, go to next step.
Allow engine to cool. Ensure coolant level is full. If coolant level is okay, go to next step. If coolant level is low, check cooling system for leaks. Repair as necessary. Retest system.
Start engine and let idle. Observe ENG COOL TEMP parameter on scan tool. If display increases to greater than 70?F (21?C) within 2 minutes, check for an intermittent problem. See TESTS W/O CODES article. If display is not as specified, go to next step.
Check thermostat for proper operation. Replace thermostat if necessary. Retest system. If thermostat is okay, go to next step.
Using a thermometer, check temperature of water in radiator. Compare reading with display on scan tool. If readings are fairly close, check for sticking thermostat or incorrect thermostat application. Repair as necessary. If display readings are not close, go to next step.

Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, measure resistance between ECT sensor signal circuit and ECT sensor ground circuit at PCM harness connector. Compare resistance reading with coolant temperature. See ENGINE COOLANT TEMPERATURE RESISTANCE table. If readings are as specified, replace PCM. Retest system. If readings are not as specified, go to next step.

Isuzu Trooper S 1996 ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE

Temperature ?F (?C)	Ohms
-40 (-40)	100,700
-22 (-30)	52,700
5 (-15)	21,450
23 (-5)	12,300
41 (5)	7280
59 (15)	4450
77 (25)	2796
95 (35)	1802
113 (45)	1188
140 (60)	667
176 (80)	332
212 (100)	177

Using an ohmmeter, check for high resistance in ECT sensor signal circuit or sensor ground circuit. Check for poor connections at PCM and ECT sensor. Repair as necessary. If ECT sensor circuit is okay, replace ECT sensor. Retest system.