Chart C-16 ECM Controlled Temp Light Circuit

Chart C-16:

Temperature Lamp Circuit:

CIRCUIT DESCRIPTION:
The TEMP light is powered through the gauges fuse by ignition voltage. The ECM energizes the bulb by supplying a path to ground through quad-driver module 1 & 2 (A).

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. With the ignition "ON" and engine "OFF," the ECM should be grounding CKT 35.

2. The TEMP light should only be "ON" while the engine is running and the coolant temperature is 120°C (248°F) or higher.

DIAGNOSTIC AIDS:
The coolant temperature sensor, in rare cases, may fail to indicate the correct engine coolant temperature without setting a malfunction code. This could result in turning "ON" the TEMP light without having an overheating condition. It could also result in overheating without the TEMP light being turned "ON." See Coolant Sensor Temperature vs. Resistance Values, Diagnostic Aids table on Code 15 chart or compare coolant temperature reading on the "SCAN" tool with actual coolant temperature. Replace coolant temperature sensor if mis-scaled.