Chart C-16 ECM Controlled Temp/Check Gauges Lamp Circuit

Chart C-16 - ECM Controlled "TEMP"/"CHECK GAUGES" Lamp Circuit:

Chart C-16 Wiring Circuit:

Circuit Description:

The "Temp"/"Check Gauges" lamp is powered through the gages fuse by ignition voltage. The ECM energizes the "Temp" lamp bulb by supplying a path to ground through quad-driver module A. If equipped with a "Check Gauges" lamp, the lamp is energized by a buffer within the cluster when an abnormal condition can be seen on a gauge or CKT 35 is grounded, indicating high engine coolant temperature.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. With the ignition "ON" and engine "OFF," the ECM should be grounding CKT 35.
2. The "Temp" lamp should only be "ON" while the engine is running and engine coolant temperature is 120°C (248°F) or higher. If equipped with a "Check Gauges" lamp, the lamp should be "ON" only if an abnormal condition can be seen on a gauge (high or low system voltage, low fuel level, low oil pressure, or CKT 35 grounded indicating high engine coolant temperature).

Diagnostic Aids:

The engine coolant temperature sensor, in rare cases, may fail to indicate the correct engine coolant temperature without setting a diagnostic trouble code. This could result in turning "ON" the "Temp" or "Check Gauges" lamp without having an overheating condition. It could also result in overheating without the "Temp" or "Check Gauges" lamp being turned "ON." See "Engine Coolant Sensor Temperature vs. Resistance Values" diagnostic aids table on DTC 15 chart or compare engine coolant temperature reading on the Tech 1 with actual engine coolant temperature. Replace engine coolant temperature sensor if mis-scaled.