Chart A2 - "Eng Control System" Light On (No Codes Present

The "ENGINE CONTROL SYSTEM" (ECS) light is powered through the 10-amp "IGN-1" fuse 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 a service message is set.

If a service trouble code is set, 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.

Intermittent loose grounds or power connections can cause ECM to repeatedly power-up, power-down or to reset.
Check for bulb grounded by ECM through pin "C1" or through a circuit fault.
Remove and replace both ECM connectors and ensure that they are latched. Check MEM-CAL unit for proper orientation, bent pins, and full seating in socket. Substitute a known good MEM-CAL unit to see if unit is causing the light to flicker. If test MEM-CAL unit does not correct condition, replace ECM. Be sure to perform CHART C1 - ECM REPLACEMENT CHECK.

Fig 1: Flow Chart A2 Schematic, "Eng Cont Syst" Lt On (No Codes Present)

Fig 2: Flow Chart A2, "Eng Cont System" Light On (No Codes Present)

Fig 3: Flow Chart A2, "Engine Control System" Light On (No Codes Present)