ECM Check CEL Doesn't Flash Code 12 Or Remains On

This check determines why the CEL remains on or does not flash Code 12. Since the CEL is remote from the ECM, it can recognize faulty ECM power or ECM.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).

Checks for proper CEL signal (approximately battery voltage) at ALCL.
Checks for 12 volts at ECM ignition feed terminals.
Checks for good ECM ground. If ECM power and ground terminals are OK, check ECM-to-connecter terminal connections.
When vehicle is started, ECM turns CEL off. Voltage at ALCL should drop below 6 volts.

Fig 1: Chart, ECM Check CEL Doesn't Flash Code 12 Or Remains On

Fig 2: Chart, ECM Check CEL Doesn't Flash Code 12 Or Remains On