Chart A1 (1 Of 2)
The "ENGINE CONTROL SYSTEM" (ECS) light is powered through the 10-amp "IGN-1" fuse No. 18 in fuse block, and grounded by ECM pin "C1" to illuminate. The ECS light will check bulb with key on. Light is illuminated steadily during cranking and is illuminated whenever a trouble code with service message is set.
If a service trouble code is set, the ECM will send a service status to BCM via the data link. At the same time, ECM grounds pin "C1" to turn on ECS light.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- If code EO18 is present, diagnose code EO18 before proceeding. The ECS light illuminates with engine cranking only if crank input is present to ECM.
- If code B334 is current ("NO ECM DATA" is displayed), go to CHART A1 (2 OF 2) to check for loss of power or ground to ECM.
- If "STOP ENGINE/OIL" light is displayed with key on/engine off, power to cluster lights is okay. Diagnose location of open ground circuit to ECS light or for blown ECS light bulb.
- Starting at ECM, this branch of chart follows circuit No. 325, grounding circuit No. 325 as ECM would do to turn bulb on. If a ground at given point on circuit No. 325 brings ECS light on, circuit from grounded point to light is okay.