#2 - Check Engine Light on and Won't Flash Code 12

There should always be a steady Malfunction Indicator Lamp (MIL) when the Ignition is "ON" and Engine stopped. Battery Ignition voltage is supplied directly to the light bulb. The Engine Control Module (ECM) will turn the light on by grounding circuit C1-22 at the ECM. With the diagnostic terminal grounded, the light should flash Diagnostic Trouble Code (DTC) 12, followed by any DTCs stored in memory.

A steady light suggests a short to ground in the light control circuit or an open in diagnostic circuit.




Test Description
Number(s) below refer to number(s) on the diagnostic chart.

1. If the light goes off when the ECM Connector is disconnected, then circuit "10" is not shorted to ground. Also, check the Connector Terminals physically for proper contact at this time.
2. This step will check for an open diagnostic circuit "24" or "69".
3. At this point the MIL wiring is okay. The problem is a faulty ECM Connector or ECM.