Electric Cooling Fan Diagnosis

Circuit Description:
The Auxiliary Cooling Fan is controlled by the VCM based on various inputs. Battery voltage is supplied to the auxiliary cooling fan relay. Ignition voltage is supplied to the auxiliary fan relay (coil side). The VCM controls the cooling fan relay by providing a ground path.

Diagnostic Aids
If the driver complaint is an overheating problem, it must be determined if the complaint was due to an actual boil over, or the warning indicator light, or Engine Coolant Temperature gauge indicated overheating. The gauge accuracy can also be checked by the Engine Coolant Temperature (ECT) sensor reading using a scan tool and comparing its reading with the gauge reading.

If the engine is overheating and the cooling fan is ON, the cooling system should be checked, refer to Cooling System.

The VCM will command the auxiliary cooling fan on at 108°C (226°F) and OFF at 102°C (215°F).

An intermittent may be caused by any of the following conditions:
^ A poor connection
^ Rubbed through wire insulation
^ A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis. Symptom Related Diagnostic Procedures

Test Description
Number(s) below refer to step numbers on the diagnostic table.
6. This test checks the control circuit for a short to ground.