AIR CONDITIONING, DESCRIPTION AND OPERATION, Operation. Operation of the cooling fan will be given priority to operate for engine cooling, overriding any request from the ATC ECU. The fan speed for engine cooling is dependant on engine coolant temperature and current road speed. The ECM will allow the cooling fan to 'run-on' after the engine is stopped. This is limited by engine coolant temperature or a maximum run-on time. If the ECT sensor fails a default value is used and the cooling fan will run permanently.
ENGINE MANAGEMENT SYSTEM – TD 18-1-38 DESCRIPTION AND OPERATION