Engine Cooling Fan Control

WARNING: This page is about a different car, the 2006 Land Rover Range Rover. However, it is still accessible from the selected car via links, so may be relevant.

The engine's electric cooling fan is controlled by the engine control module ECM. When the A/C compressor is engaged the ATC module sends a fan speed message between 0 (off) and 15 (maximum speed) to the ECM, via the K bus, instrument cluster and high speed controller area network CAN bus. The ATC module requests the cooling fan on when:

The vehicle speed is less than 70 km/h (44 mph).
There is no fault with the A/C compressor clutch circuit.
Battery voltage is less than 16 V.

The fan speed requested depends on the pressure in the refrigerant system. The higher the pressure the faster the fan speed that is requested. When vehicle speed increases to more than 80 km/h (50 mph) the ATC module changes the fan speed request to 0 until vehicle speed decreases to less than 70 km/h (44 mph) again.

If battery voltage increases to more than 16 V for 5 seconds the ATC module changes the fan speed to 0 until the voltage decreases to less than 15.8 V.