Chart C-16 ECM/PCM Controlled Temp Light Circuit

Chart C-16:

Chart C-16 Wiring Diagram:

CIRCUIT DESCRIPTION:

***UPDATED BY TSB # 91-6E-7 DATED FEBRUARY 1991

The Coolant Level Sensor is a solid state module that monitors coolant level. It is located at the right hand radiator tank, and senses coolant by means of two probes that protrude into the coolant.

When the coolant is at the proper level, the coolant level signal at the ECM is pulled low (0-3 volts). When the coolant level is low, the signal at the ECM will be high (4-5 volts) and the ECM will turn "ON" the low coolant light.


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 circuit 35.

2. The TEMP light should only be controlled to be turned "ON" while the engine is running when the coolant temperature is above 123°C (253°F).


DIAGNOSTIC AIDS

The coolant temperature sensor in rare cases, may fail to indicate the correct engine coolant temperature without setting a trouble code. This could result in turning "ON" the "TEMP" light without having a overheating condition. It could also result in overheating without the "TEMP" light being turned "ON." See coolant sensor temperature vs resistance values on trouble Code diagnostic chart Code 15. Compare coolant temperature reading from scanner to this chart. Replace coolant temperature sensor if mis-scaled.