"Hot" Coolant Light

Wiring Diagram:

CIRCUIT DESCRIPTION

The ECM provides and internally monitors voltage to the engine coolant temperature sensor circuit through pin 2B9. As the coolant temperature goes from cold to hot, the sensor's resistance goes from high to low, and the voltage level that the ECM detects at pin 2B9 goes from high to low. Every 1 second, the BCM checks the ECM for the coolant temperature. If the calculated coolant temperature reaches 126 degrees centigrade (i.e. the voltage at pin 2B9 of the ECM drops low enough), and all other failure conditions are met, the BCM will cause the HOT Coolant light on the Instrument Panel Cluster (IPC) to come on. Refer to Cooling System / System Diagnosis.

TEST CONDITION(S)

1. Engine is running.

2. Coolant temperature not failed.

3. No data line codes set.

FAILURE CONDITION(S)

1. Engine coolant temperature greater than 126 degrees centigrade.

OR

1. ENGINE OVERHEAT condition already present

2. Engine coolant temperature greater than 120 degrees centigrade

ACTION TAKEN

1. Turn on HOT telltale on IPC.

DIAGNOSIS

1. Condition
^ Erroneous Message

Possible Causes
^ Short to ground on CKT 410 or
^ shorted switch

2. Condition
^ No Message Open in CKT 410, CKT 452, or
^ open in switch

Possible Causes
^ Open in CKT 410, CKT 452, or
^ open in switch