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 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 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).