SELF-DIAGNOSTIC SYSTEM
| Application | Figure |
|---|---|
| Diagnostic Circuit Check | 4 |
| ECM Terminal Identification | 3 |
| Trouble Code Charts | 12-48 |
SELF-DIAGNOSTICS DIRECTORY
TROUBLE CODE DEFINITION
| Code | System Affected | Probable Cause |
|---|---|---|
| 12 | System Normal | System Normal |
| 13 | O2 Sensor Circuit | Sensor/Circuit, ECM |
| 14 | Coolant Temperature Sensor (Shorted) | Temperature Sensor/ Circuit, ECM |
| 15 | Coolant Temperature Sensor (Open) | Temperature Sensor/ Circuit, ECM |
| 21 | Throttle Valve Switch (Idle & Full Throttle) | Temperature Sensor/ Circuit, ECM |
| 22 | Starter Signal | Circuit, ECM |
| 23 | Power Transistor (Shorted) | Transistor/Circuit ECM |
| 25 | Pressure Regulator VSV | VSV/Circuit, ECM |
| 26 | Canister Purge VSV | VSV/Circuit, ECM |
| 27 | Canister Purge VSV | VSV/Circuit, ECM |
| 32 | EGR System | EGR Valve, Backpressure Transducer, Vacuum Switching Valve |
| 33 | Fuel Injector Circuit (Open or Grounded) | Wiring, Dropping Resistor, ECM |
| 34 | EGR Temperature Sensor | Sensor/Circuit, ECM |
| 35 | Power Transistor (Open) | Transistor/Circuit, ECM |
| 41 | Crank Angle Sensor | Sensor/Circuit, ECM |
| 43 | Throttle Valve Switch (Idle Position) | Switch/Circuit, ECM |
| 44 | O2 Sensor (Lean/Rich) | Injectors, Fuel Pressure, Airflow Sensor, O2 Sensor Circuit, Coolant Temperature Sensor, ECM |
| 45 | O2 Sensor (Lean/Rich) | Injectors, Fuel Pressure, Airflow Sensor, O2 Sensor Circuit, Coolant Temperature Sensor, ECM |
| 51 | Faulty ECM ROM | Defective ECM |
| 52 | Faulty ECM RAM | Defective ECM |
| 53 | Pressure Regulator VSV | VSV/Circuit, ECM |
| 54 | Power Transistor (Grounded) | Transistor/Circuit ECM |
| 61 | Airflow Sensor | Sensor/Circuit, ECM |
| 62 | Airflow Sensor | Sensor/Circuit, ECM |
| 63 | Vehicle Speed Sensor | Sensor/Circuit, ECM |
| 64 | Fuel Injector Circuit (ECM Transistor) | Wiring Harness, ECM |
| 65 | Throttle Valve Switch (Full Throttle) | Switch/Circuit, ECM |
TROUBLE CODE IDENTIFICATION
Diagnostic Circuit Check Courtesy Isuzu Motor Co. Scheme 28
Inspection & Correction
- If battery voltage is not present at terminals No. 1, 14 and 4, check main relay, starter switch, fuses, fusible link wires and related circuits. Correct or replace parts as necessary.
- If continuity does not exist between terminals No. 11 and 22, correct or replace grounding cable.
- Reconnect ECM harness connectors.
Test No. 1 - ECM Power Supply Courtesy Isuzu Motor Co. Scheme 29
TEST NO. 2 - CHECK ENGINE LIGHT INOPERATIVE
Note. Before replacing ECM, check resistance of ECM-controlled relay and solenoid coils. See appropriate wiring diagram in WIRING DIAGRAM article for coil terminal identification of solenoids and relays. Replace any solenoid or relay with less than 20 ohms resistance.
Airflow Sensor Connector Courtesy Isuzu Motor Co. Scheme 30
Data Link Connector Courtesy Isuzu Motor Co. Scheme 31
Test No. 2 - Diagnostic Flowchart Courtesy Isuzu Motor Co. Scheme 32
TEST NO. 3 - WILL NOT FLASH CODE 12
Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.
Test No. 3 - Diagnostic Flowchart Courtesy Isuzu Motor Co. Scheme 33
Fuel Metering Rich Faulty Inspection Procedure
Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.
Fuel Metering Rich - Diagnostic Flowchart Courtesy Isuzu Motor Co. Scheme 34
Fuel Metering Lean Faulty Inspection Procedure
Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.
