Isuzu Pickup 1 Ton 1991 - 1991-92 ENGINE PERFORMANCE Self-Diagnostics - Amigo & Pickup - 2.3L Carbureted

Isuzu Pickup 1 Ton 1991 - INTRODUCTION

If no faults were found while performing appropriate BASIC TESTING article in the ENGINE PERFORMANCE Section proceed with self-diagnostics. If no fault codes or only pass codes are present after entering self-diagnostics, proceed to appropriate TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptom (i.e. ROUGH IDLE, NO START, etc.).

Isuzu Pickup 1 Ton 1991 - SELF-DIAGNOSTIC SYSTEM HARD FAILURES

Hard failures cause CHECK ENGINE light to illuminate and remain on until problem is repaired. If light comes on and remains on (light may flash) during vehicle operation, determine cause of malfunction using diagnostic (code) charts. If a sensor fails, Electronic Control Module (ECM) will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, the vehicle runs but driveability will not be optimum.

Isuzu Pickup 1 Ton 1991 - INTERMITTENT FAILURES

Intermittent failures may cause CHECK ENGINE light to flicker or illuminate and go out after intermittent fault goes away. However, the corresponding trouble code will be stored in ECM memory. If related fault does not reoccur within a certain time frame, related trouble code will be erased from ECM memory. Intermittent failures can be caused by a faulty sensor, connector or wiring. See INTERMITTENTS in appropriate TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

Fig. 1: Isuzu Pickup 1 Ton 1991 - Component Locations - Locating ECM & Diagnostic Connector

Isuzu Pickup 1 Ton 1991 - RETRIEVING CODES

1. Code retrieval starts with the DIAGNOSTIC CIRCUIT CHECK. The CHECK ENGINE light comes on when ignition is on and engine is not running. When engine starts, CHECK ENGINE light should go off. If light remains on while engine is running, a trouble code is present.
2. If light did not come on with key on and engine off, inspect CHECK ENGINE light circuit before continuing. If CHECK ENGINE light fails to operate, see DIAGNOSTIC CIRCUIT CHECK. Circuit checks are located within code charts.
3. To retrieve codes, install jumper wire between White and Black wires of ALDL diagnostic connector, located behind left kick panel near ECM. See Fig. 1 .

   NOTE:

   Diagnostic connector may also be referred to as ALDL test lead.

4. Turn ignition on and count number of flashes from CHECK ENGINE light. A Code 12 will be a flash, pause and flash, flash. A long pause will occur. Code 12 will repeat 3 times. See Fig. 2 . Each additional code will flash 3 times, starting with lowest number code to the highest number code. Once all codes are displayed, codes will be repeated.
5. If system is operating properly (with no codes), a Code 12 should exist with ignition on and engine off. This indicates diagnostic system is working. Remove jumper wire from ALDL diagnostic connector after codes are retrieved.

Fig. 2: Isuzu Pickup 1 Ton 1991 - Component Locations - Code Display (Typical)

Isuzu Pickup 1 Ton 1991 - CLEARING TROUBLE CODES

CAUTION:

Ensure ignition is off when disconnecting or reconnecting power to ECM.

1. After performing repairs, clear ECM memory of stored trouble codes. To clear memory, turn ignition off. Remove 60-amp MAIN fuse from fuse block, located in left front corner of engine compartment, for at least 10 seconds. Replace fuse.
2. Trouble codes can also be cleared by disconnecting negative battery cable. However, other memory functions (clock, radio, etc.) will then require resetting.

NOTE:

Codes will also erase if problem does not reoccur within 50 engine starts.

Isuzu Pickup 1 Ton 1991 ECM LOCATIONS

Model	Location
Amigo & Pickup	On left kick panel

Isuzu Pickup 1 Ton 1991 - CODE CHARTS TROUBLE CODE IDENTIFICATION

Isuzu Pickup 1 Ton 1991 TROUBLE CODE IDENTIFICATION

Code No.	System Affected	Probable Cause
12 (1)	Ignition Ref. Signal	Dist. or Circuit, ECM
13 (2)	O2 Sensor	Sensor/Circuit, ECM
14 (3)	Shorted Coolant Temp. Sensor Signal	Sensor/Circuit, ECM
15 (4)	Open Coolant Temp. Sensor Signal	Sensor/Circuit, ECM
21 (5)	Idle (Vacuum) Switch & MAP Sensor	Switch/Circuit, ECM
22 (6)	Fuel-Cut Solenoid	Relay/Circuit, ECM
23	Duty (Mixture Control) Solenoid Circuit	Solenoid Circuit, ECM
25	AIR Management Valve	VSV/Valve Circuit, ECM
26	Canister Purge VSV	VSV/Valve Circuit, ECM
27	Canister Purge VSV	VSV/Valve Circuit, ECM
31 (2) (7)	Ignition Ref. Signal	Wiring Circuit, ECM
32	EGR System	EGR Valve, Thermal Vac. Valve or Backpressure Transducer
34	EGR Gas Temp. Sensor	Sensor/Circuit, ECM
44 (2) (8)	O2 Sensor (Lean)	Mixture Control Solenoid, O2 Sensor, ECM
45 (2) (9)	O2 Sensor (Rich)	Mixture Control Solenoid, O2 Sensor, ECM
51	Fuel-Cut Solenoid	Solenoid/Circuit, ECM
52	Faulty ECM RAM	ECM
53	AIR Management Valve	Valve or ECM
54	Mixture Control Solenoid	Solenoid/Circuit, ECM
55	Faulty ECM	ECM
(1) Code 12 is a normal response to key on and engine off with ALDL test lead installed. (2) Requires engine operation at part throttle under load for up to 5 minutes after engine reaches normal operating temperature to set code. (3) Engine must be running at least 2 minutes before code will be set. (4) Engine must be running at least 5 minutes before code will be set. (5) Code will set if one of following conditions exist: Engine speed is 200-1000 RPM and vacuum applied to MAP sensor is more than 20 in. Hg for 5 seconds; Idle switch is off and vacuum applied to MAP sensor is less than 4 in. Hg for 5 seconds.; Engine speed is greater than 1500 RPM and vacuum applied to MAP sensor is 16-18 in. Hg and idle switch is on for 5 seconds. (6) Engine must be decelerating and engine speed greater than 2000 RPM before code will be set. (7) No reference signal to ECM after 10 seconds at part throttle under load. Code will be stored in memory. (8) Engine speed must be less than 2500 RPM and exist for 5 seconds after fuel-cut recovery. Code will set except when vacuum reading to MAP sensor is less than 23 in. Hg, Code 13 or 21 is stored, or coolant temperature is greater than 302?F (150?C). (9) Engine speed must be less than 2500 RPM with vehicle speed of 12-50 MPH for more than 30 seconds after canister purge. Code will set except when vacuum reading to MAP sensor is less than 23 in. Hg, Code 13 or 21 is stored, coolant temperature is greater than 302?F (150?C) or under high altitude conditions greater than 8000 ft. (2434 meters).

Isuzu Pickup 1 Ton 1991 - ECU TERMINAL IDENTIFICATION

CAUTION:

Perform all voltage measurements with ECU harness connector installed.

Fig. 3: Isuzu Pickup 1 Ton 1991 - Component Locations - ECU Terminal ID (Back View With Connector Installed)

Fig. 4: Isuzu Pickup 1 Ton 1991 - Component Locations - ECU Terminal ID (Front View With Connector Removed)

Isuzu Pickup 1 Ton 1991 - DIAGNOSTIC CIRCUIT CHECK

Fig. 5: Isuzu Pickup 1 Ton 1991 - Component Locations - Diagnostic Circuit Check

Isuzu Pickup 1 Ton 1991 - TEST NO. 1 - CHECK ENGINE LIGHT INOPERATIVE

Fig. 6: Isuzu Pickup 1 Ton 1991 - Component Locations - Test No. 1 Schematic, Check Engine Light Inoperative

Fig. 7: Isuzu Pickup 1 Ton 1991 - Component Locations - Test No. 1 Flow Chart, Check Engine Light Inoperative

Isuzu Pickup 1 Ton 1991 - TEST NO. 2 - WILL NOT FLASH CODE NO. 12

Fig. 8: Isuzu Pickup 1 Ton 1991 - Component Locations - Test No. 2 Flow Chart, Won't Flash Code No. 12

Isuzu Pickup 1 Ton 1991 - CODE 12 - IGNITION REFERENCE SIGNAL

NOTE:

To check ignition system components, see IGNITION SYSTEM in appropriate I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

Fig. 9: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 12 Schematic, Ignition Reference Signal

Fig. 10: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 12 Flow Chart, Ignition Reference Signal

Isuzu Pickup 1 Ton 1991 - CODE 13 - OXYGEN SENSOR CIRCUIT

NOTE:

If Codes 13 and 23 exist, start with Code 23.

Fig. 11: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 13 Schematic, Oxygen Sensor Circuit

Fig. 12: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 13 Flow Chart, Oxygen Sensor Circuit

Isuzu Pickup 1 Ton 1991 - CODE 14 - SHORTED COOLANT TEMPERATURE SENSOR SIGNAL

Fig. 13: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 14 Schematic, Shorted Coolant Temp. Sensor Signal

Fig. 14: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 14 Flow Chart, Shorted Coolant Temp. Sensor Signal

Isuzu Pickup 1 Ton 1991 - CODE 15 - OPEN COOLANT TEMPERATURE SENSOR SIGNAL

Fig. 15: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 15 Schematic, Open Coolant Temp. Sensor Signal

Fig. 16: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 15 Flow Chart, Open Coolant Temp. Sensor Signal

Isuzu Pickup 1 Ton 1991 - CODE 21 - IDLE (VACUUM) SWITCH & MAP SENSOR

NOTE:

If Codes 21 and 23 exist, start with Code 23.

Fig. 17: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 21 Schematic, Idle (Vacuum) Switch & MAP Sensor

Fig. 18: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 21 Flow Chart, Idle (Vacuum) Switch & MAP Sensor

Isuzu Pickup 1 Ton 1991 - CODE 22 & 51 - FUEL-CUT SOLENOID CIRCUIT

Fig. 19: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 22, 51 Schematic, Fuel-Cut Solenoid Circuit

Fig. 20: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 22, 51 Flow Chart, Fuel-Cut Solenoid Circuit

Isuzu Pickup 1 Ton 1991 - CODE 23 & 54 - DUTY (MIXTURE CONTROL) SOLENOID CIRCUIT

Fig. 21: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 23, 54 Schematic, Duty Solenoid Circuit

Fig. 22: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 23, 54 Flow Chart, Duty Solenoid Circuit

Isuzu Pickup 1 Ton 1991 - CODE 25 & 53 - AIR MANAGEMENT VALVE CIRCUIT

Fig. 23: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 25, 53 Schematic, Air Management Valve Circuit

Fig. 24: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 25, 53 Flow Chart, Air Management Valve Circuit

Isuzu Pickup 1 Ton 1991 - CODE 26 & 27 - CANISTER PURGE VSV CIRCUIT

Fig. 25: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 26, 27 Schematic, Canister Purge VSV Circuit

Fig. 26: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 26, 27 Flow Chart, Canister Purge VSV Circuit

Isuzu Pickup 1 Ton 1991 - CODE 31 - IGNITION REFERENCE SIGNAL

Fig. 27: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 31 Schematic, Ignition Reference Signal

Fig. 28: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 31 Flow Chart, Ignition Reference Signal

Isuzu Pickup 1 Ton 1991 - CODE 32 - EGR SYSTEM MALFUNCTION Specified Reappearance Pattern

1. Run engine at idle condition, at normal operating temperature.
2. Keep at idle for more than 10 seconds, with vehicle stopped
3. Drive vehicle at just over 10 MPH. Accelerate quickly to more than 30 MPH (must reach 30 MPH within 10 seconds of starting acceleration).
4. Within 30 seconds, decelerate safely to a complete stop. See Fig. 29 .
5. Repeat above procedure 2) through 4) several times.

Fig. 29: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 32 Acceleration Chart

Fig. 30: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 32 Component Diagram, EGR System Malfunction

Fig. 31: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 32 Flow Chart, EGR System Malfunction

Isuzu Pickup 1 Ton 1991 - CODE 34 - EGR GAS TEMPERATURE SENSOR

Isuzu Pickup 1 Ton 1991 EGR GAS TEMP SENSOR RESISTANCE

Temperature ?C (?F)	Resistance Ohms
0 (32)	28000
20 (68)	12100
40 (109)	5800
80 (176)	1700

Fig. 32: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 34 Schematic, EGR Gas Temp. Sensor

Fig. 33: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 34 Flow Chart, EGR Gas Temp. Sensor (1 of 2)

Fig. 34: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 34 Flow Chart, EGR Gas Temp. Sensor (2 of 2)

Isuzu Pickup 1 Ton 1991 - CODE 44 - OXYGEN SENSOR-LEAN FUEL MIXTURE

1. Disconnect oxygen sensor connector. With ignition ON and engine stopped, check for repeated clicks from duty solenoid.
2. If there are repeated clicks, repair carburetor. If no repeated clicks are heard, replace duty solenoid.

Fig. 35: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 44 Schematic, O2 Sensor-Lean Fuel Mixture

Fig. 36: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 44 Harness Diagram, O2 Sensor-Lean Fuel Mixture

Fig. 37: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 44 Flow Chart, O2 Sensor-Lean Fuel Mixture

Isuzu Pickup 1 Ton 1991 - CODE 45 - OXYGEN SENSOR-RICH FUEL MIXTURE

NOTE:

A restricted air cleaner can cause a Code 45.

1. Disconnect oxygen sensor connector. With ignition ON and engine stopped, check for repeated clicks from duty solenoid.
2. If there are repeated clicks, repair carburetor. If no repeated clicks are heard, replace duty solenoid.

Fig. 38: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 45 Schematic, O2 Sensor-Rich Fuel Mixture

Fig. 39: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 45 Harness Diagram, O2 Sensor-Rich Fuel Mixture

Fig. 40: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 45 Flow Chart, O2 Sensor-Rich Fuel Mixture

Isuzu Pickup 1 Ton 1991 - CODE 51 - FUEL-CUT SOLENOID CIRCUIT

See Code No. 22.

Isuzu Pickup 1 Ton 1991 - CODE 52 - FAULTY ECM RAM

Fig. 41: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 52 Flow Chart, Faulty ECM Ram

Isuzu Pickup 1 Ton 1991 - CODE 53 - AIR SWITCHING VALVE VSV OR ECM

See Code No. 25.

Isuzu Pickup 1 Ton 1991 - CODE 54 - DUTY (MIXTURE CONTROL) SOLENOID CIRCUIT

See Code No. 23.

Isuzu Pickup 1 Ton 1991 - CODE 55 - FAULTY ECM

Fig. 42: Isuzu Pickup 1 Ton 1991 - Component Locations - Code No. 55 Flow Chart, Faulty ECM

Isuzu Pickup 1 Ton 1991 - SUMMARY

If no hard fault codes (or only pass codes) are present, driveability symptoms exist or intermittent codes exist, proceed to appropriate TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptom (i.e. ROUGH IDLE, NO START, etc.), or intermittent diagnosis procedures.