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.).
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.
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.
Scheme 25
RETRIEVING CODES
- 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.
- 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.
- To retrieve codes, install jumper wire between White and Black wires of ALDL diagnostic connector, located behind left kick panel near ECM. (Scheme 25) NOTE: Diagnostic connector may also be referred to as ALDL test lead.
- 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. (Scheme 26) 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.
- 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.
Scheme 26
CLEARING TROUBLE CODES
| CAUTION | Ensure ignition is off when disconnecting or reconnecting power to ECM. |
- 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.
- 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.
| Model | Location |
|---|---|
| Amigo & Pickup | On left kick panel |
ECM LOCATIONS
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). | ||
| (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). |
TROUBLE CODE IDENTIFICATION
ECU TERMINAL IDENTIFICATION
| CAUTION | Perform all voltage measurements with ECU harness connector installed. |
Scheme 27
Scheme 28
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Scheme 31
Scheme 32
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.
Scheme 33
Scheme 34
CODE 13 - OXYGEN SENSOR CIRCUIT
Note. If Codes 13 and 23 exist, start with Code 23.
Scheme 35
Scheme 36
Scheme 37
Scheme 38
Scheme 39
Scheme 40
CODE 21 - IDLE (VACUUM) SWITCH & MAP SENSOR
Note. If Codes 21 and 23 exist, start with Code 23.
Scheme 41
Scheme 42
Scheme 43
Scheme 44
Scheme 45
Scheme 46
Scheme 47
Scheme 48
Scheme 49
Scheme 50
Scheme 51
Scheme 52
Specified Reappearance Pattern
- Run engine at idle condition, at normal operating temperature.
- Keep at idle for more than 10 seconds, with vehicle stopped
- Drive vehicle at just over 10 MPH. Accelerate quickly to more than 30 MPH (must reach 30 MPH within 10 seconds of starting acceleration).
- Within 30 seconds, decelerate safely to a complete stop. (Scheme 53)
- Repeat above procedure 2) through 4) several times.
Scheme 53
Scheme 54
Scheme 55
CODE 34 - EGR GAS TEMPERATURE SENSOR
| Temperature °C (°F) | Resistance Ohms |
|---|---|
| 0 (32) | 28000 |
| 20 (68) | 12100 |
| 40 (109) | 5800 |
| 80 (176) | 1700 |
EGR GAS TEMP SENSOR RESISTANCE
Scheme 56
Scheme 57
Scheme 58
CODE 44 - OXYGEN SENSOR-LEAN FUEL MIXTURE
- Disconnect oxygen sensor connector. With ignition ON and engine stopped, check for repeated clicks from duty solenoid.
- If there are repeated clicks, repair carburetor. If no repeated clicks are heard, replace duty solenoid.
Scheme 59
Scheme 60
Scheme 61
CODE 45 - OXYGEN SENSOR-RICH FUEL MIXTURE
Note. A restricted air cleaner can cause a Code 45.
- Disconnect oxygen sensor connector. With ignition ON and engine stopped, check for repeated clicks from duty solenoid.
- If there are repeated clicks, repair carburetor. If no repeated clicks are heard, replace duty solenoid.
Scheme 62
CODE 51 - FUEL-CUT SOLENOID CIRCUIT
See Code No. 22.
Scheme 63
CODE 53 - AIR SWITCHING VALVE VSV OR ECM
See Code No. 25.
CODE 54 - DUTY (MIXTURE CONTROL) SOLENOID CIRCUIT
See Code No. 23.
Scheme 64
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.