ENGINE COOLING FAN LOW SPEED
The engine cooling fan low speed relay is energised by the BCM. The PCM determines when to enable the low speed fan based on inputs from the BCM serial data, Engine Coolant Temperature (ECT) sensor and the Vehicle Speed Sensor (VSS). The cooling fan low speed relay will be turned "ON'' when:
. The A/C request indicated (YES) and either the vehicle speed is less than 30 km/h
- OR -
. A/C pressure is greater than 1500 kPa
- OR -
. The coolant temperature is greater than 104 degrees C.
If the coolant temperature is greater than 117 degrees C when the ignition is switched off, the relay is energised for up to approximately 4 minutes.
If an engine coolant temperature sensor fault is detected, such as DTC 14, 15, 16, 17 or 91.
The cooling fan low speed relay will be turned "OFF'' when any of the following conditions have been met:
. The A/C request is not indicated (NO)
. The A/C request is indicated (YES) and the vehicle speed is greater than 50 km/h and A/C pressure is less than 1170 kPa.
ENGINE COOLING FAN HIGH SPEED
The engine cooling fan high speed relay is controlled by the PCM based on input from the Engine Coolant Temperature (ECT) sensor. The PCM will only turn "ON'' the engine cooling fan high speed relay fan if the engine cooling fan low speed relay has been "ON" for 2 seconds and the following conditions are satisfied:
. There is a BCM message response fault which will cause a DTC 92
. An engine coolant temperature sensor fault is detected such as DTC 14,15,16,17.
. Coolant temperature greater than 104 degrees C.
The engine cooling fan high speed relay can also be enabled by the A/C Refrigerant Pressure Sensor. When the A/C Refrigerant Pressure Sensor determines the A/C system pressure is to high, greater than 2600 kPa, and this will instruct the PCM to enable the high speed fan.
If the low speed fan was "OFF" when the criteria was met to turn the high speed fan "ON", the high speed fan will come "ON" 5 seconds after the low speed fan is turned "ON". "
If both the engine cooling fan relays are "ON", the PCM will turn "OFF" the high speed relay when:
. The engine coolant temperature is less than 99 degrees C.
. A/C request not indicated (NO)
. A/C request indicated (YES) and A/C pressure is less than 2300 kPa.