[amidgeha]

Fan Rationality Check

The electric cooling fan is controlled by the Engine Control Module (ECM) through the cooling fan relay based on inputs from the following components:

- The engine coolant temperature (ECT) sensor

- The intake air temperature (IAT) sensor

- The A/C selector switch

- The A/C refrigerant pressure sensor

- The vehicle speed sensor (VSS)

The ECM controls the cooling fan by grounding the cooling fan control circuit which turns ON the cooling fan relay. The cooling fan relay will be commanded ON when the following conditions are met:

- The engine coolant temperature reaches 106°C (223°F) or more.

- The A/C clutch requested.

- The vehicle speed is less than 38 MPH.

The cooling fan relay will be commanded ON regardless of vehicle speed when the following conditions are met:

- The engine coolant temperature is 151°C (304°F) or more.

- The A/C refrigerant pressure is high.

The cooling fan may be commanded ON when the engine is not running under a fan run-on conditions described in the electric cooling fan general description portion of the service manual.

Cause:
Faulty fan control relay
Faulty cooling fan
Fan control relay harness is open or shorted
Fan control relay circuit poor electrical connection
Fan cooling fan harness is open or shorted
Fan cooling fan circuit poor electrical connection

Symptoms:
Check engine light
Engine overheating