Entering Diagnostic Mode
- Turn ignition "ON" (engine off). The "CHECK ENGINE" lamp should glow. Locate 12-terminal Assembly Line Data Link (ALDL) connector. Connector is located on underside of instrument panel center portion. A trouble code test terminal is located in the ALDL connector and a ground terminal is located next to it. See Fig 1 . Jumper the test terminal to ground.
- The "CHECK ENGINE" lamp should flash code "12". Code "12" consists of one flash, a short pause, then 2 flashes. A longer pause will follow, then Code "12" will repeat 2 more times. Code "12" is not a trouble code. This check indicates that the self-diagnostic system is working.
- If any trouble codes are stored in ECM memory, the "CHECK ENGINE" lamp will flash 2-digit codes. If more than one fault is stored in the ECM memory, the lowest number code will flash 3 times, followed by the next highest code number, until all faults have been displayed (flashed). The faults will then repeat in the same order.
- A trouble code indicates a fault in a given circuit. The "CHECK ENGINE" lamp will only be on if the malfunction exists under conditions listed in ECM Trouble Code Identification chart.
- If the malfunction clears, the lamp will go out and a trouble code will be set in the ECM. If the lamp comes on intermittently, but no code is stored, go to the Driver Comment section. Any codes stored will be erased if no fault reoccurs within 50 engine starts.
- Faults indicated by trouble codes "13", "31", "44" and "45" require that the engine be operated at part throttle for up to 5 minutes after engine warm-up, before the "CHECK ENGINE" lamp will come on and store a trouble code. The fault indicated by trouble code "15" takes 5 minutes of engine operation before it will display. Remove ground from test terminal before starting engine.