Chart A-2, Service Engine Soon Light Will Not Go Out Or Flash - TORONADO & TROFEO
The SERVICE ENGINE SOON light is attached to the IPC. It is powered by circuit No. 39. PCM completes the ground to turn the light on. The light will be on while engine is not running. With the engine running, a steady light indicates a fault code is set. See Figure.
NOTE:
Test numbers refer to numbers on diagnostic chart.
- If the light goes off when PCM connector is unplugged, PCM drive circuit is not shorted to ground.
- If there is a problem with PCM that causes a "Scan" tester to not read serial data, PCM should not flash Code 12. If Code 12 does flash, be sure that the tester is working properly by trying it on another vehicle. If tester is working properly and circuit No. 800 is okay, MEM-CAL or PCM or another component which uses the serial data line may be at fault for the NO ALDL problem.
- This step will check for an open diagnostic circuit No. 451 (terminal "B" of ALDL).
- At this point, SERVICE ENGINE SOON light wiring is okay. The problem is a faulty PCM or MEM-CAL. If Code 12 does not flash, PCM should be replaced using original MEM-CAL. Replace MEM-CAL only after trying a PCM, as a defective MEM-CAL is an unlikely cause of the problem.