For 1990-2009 cars

The electric cooling fan(s) are used to cool engine coolant flowing through the radiator. They are also used to cool the refrigerant flowing through the A/C condenser.

The electric cooling fan(s) are controlled by the Body Control Module (BCM). The BCM controls the PCM which enables the ground path for the three cooling fan relays. The relay(s) are used to control the high current flow to power the cooling fan motors. When minimum cooling is required, the BCM will command the PCM to energize cooling fan relay #1 and since both fans are connected in series through the Mode Control relay, both fans will operate at low speed. When maximum cooling is required, the PCM energizes all three cooling fan relays. Power is supplied to the left fan through cooling fan relay #1 and is grounded through the Mode Control relay. The right fan is powered directly through cooling fan relay #2 causing both fans to operate at high speed.

### Low Speed Cooling Fans

The low speed cooling fans are controlled by the BCM based on the following inputs:

• | The A/C system.

• | The Engine Coolant Temperature (ECT) sensor.

• | The Vehicle Speed Sensor (VSS).

The BCM or the PCM will turn the low speed cooling fans ON when any of the following conditions exist at idle:

• | Certain PCM Diagnostic Trouble Codes (DTCs) are set.

• | ECT above 106°C (223°F) will enable low speed fans.

Once the low speed fans are turned ON by Engine Coolant Temperature , the BCM will command the PCM to turn the fans OFF when that temperature has dropped about 3°C (5°F).

### High Speed Cooling Fans

The High Speed Cooling Fans are controlled by the BCM based on the following inputs:

• | The A/C system

• | The Engine Coolant Temperature (ECT) sensor

• | The Vehicle Speed Sensor (VSS).

The BCM will command the PCM to turn the secondary cooling fan ON when any of the following conditions exist at idle:

• | Certain PCM Diagnostic Trouble Codes (DTCs) set.

• | ECT above 111°C (232°F).

Once the high speed cooling fans are turned ON by the Engine coolant temperature, the BCM will command the PCM to turn the fans OFF when that temperature has dropped about 3°C (5°F).

The driver side of the cooling fan relays (Coil side of relay) will be diagnosed using DTCs P0480 and P0481. Refer to Electric Cooling Fan Diagnosis for the contact side of the fan circuit.