Cooling Fan Description and Operation

Cooling Fan Description and Operation

Cooling Fan Control

The engine cooling fan system consists of one cooling fan and one relay. The relay is powered by the battery positive voltage circuit and controlled by a switched ground from the engine control module (ECM).

During operation, the ECM supplies the ground path for the cooling fan relay, which is relay 1, through the cooling fan relay control circuit. This energizes the cooling fan relay coil, closes the relay contacts, and supplies battery positive voltage from the cooling fan fuse through the cooling fan motor supply voltage circuit to the cooling fan. The cooling fan motor is grounded through its own ground circuit.

The ECM commands the fan ON under the following conditions:

* The engine coolant temperature (ECT) exceeds approximately 106°C (223°F).
* The A/C refrigerant pressure exceeds 1 310 kPa (190 psi).
* The A/C is requested and vehicle speed is below 100 km/h (62 mph) with A/C pressure above 1 413 kPa (205 psi).
* The AF23-5 transmission fluid temperature exceeds 130°C (266°F).
* The VT25-E transmission fluid temperature exceeds 140°C (284°F).
* When the ECT exceeds 100°C (212°F) at key OFF, the fan will run for up to 108 seconds.

The ECM commands the fan OFF under the following conditions:

* The ECT drops below approximately 100°C (212°F).
* The throttle position is greater than 95 percent.
* Vehicle speed exceeds 113 km/h (70 mph).

When the request for fan activation is withdrawn, the fan may not turn OFF until the ignition switch is moved to the OFF position or the vehicle speed exceeds approximately 10 mph. This is to prevent a fan from cycling ON and OFF excessively at idle.