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
Function Controller (BFC). The The BFC 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 BFC 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 BFC based on the following
inputs:
| • | The Engine Coolant Temperature (ECT) sensor. |
| • | The Vehicle Speed Sensor (VSS). |
The BFC 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 BFC 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 BFC based on the following
inputs:
| • | The Engine Coolant Temperature (ECT) sensor |
| • | The Vehicle Speed Sensor (VSS). |
The BFC 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 BFC 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.
On-Vehicle Service
When a replacement of a cooling fan relay is
necessary, the following relay(s) can be found in the under hood electrical
center:
| • | Fan control relay #1 (4). |
| • | Fan control relay #2 (2). |
| • | Mode control relay (3). |
Engine cooling system component replacement can be found in the Cooling System
portion of the service manual.
