Operation

The Engine Coolant Fan Motor #1 receives power from a 40 amp maxifuse. The Engine Coolant Fan Motor #2 receives power from a 30 amp maxifuse. Both maxifuses are located in the Underhood Electrical Center.

During low speed operation, the PCM supplies a ground path for the Cool Fan 1 relay through the Low Speed Fans control circuit. This energizes the relay coil, closes the Fan 1 relay contacts, and supplies current to engine cooling fan #1 motor. The ground path for engine cooling fan #1 is through the series/parallel cooling fan relay (Cool Fan 2 Relay) and engine cooling fan #2 motor. The result is a series circuit with both fans running at low speed.

To command high speed cooling fan operation, the PCM first supplies a ground path for the low speed cooling fan (Cool Fan 1) relay through the Low Speed Fans Control circuit. After a 3 seconds delay, the PCM supplies a ground path for the series/parallel (Cool Fan 2 Relay) and the high speed cooling fan (Cool Fan #3) relays through the High Speed Fans Control circuit. During high speed operation, both the engine cooling fans are supplied current from through their respective maxifuse and each fan has its own ground.

IMPORTANT: When certain Diagnostic Trouble Codes (DTCs) are present, the PCM may command the cooling fans to run all the time. It is important to perform the Powertrain On-Board Diagnostic System check prior to diagnosing the engine cooling fans. The PCM will complete the ground path for cooling fan relay #1 under any of the following conditions:
^ When engine coolant temperature exceeds 106°C (223°F).
^ When A/C is requested and ambient temperature is greater than 50°C (122°F).
^ When A/C refrigerant pressure is greater than 190 psi (2 volts).
^ When the ignition is off and engine coolant temperature is greater than 140°C (284°F).

For high speed cooling tans operation, the PCM will delay control of the Cool Fan 2 Relay and Cool Fan #3 relay for 3 seconds. The 3 second delay ensures that the cooling fan electrical load will not exceed the capacity of the system. The PCM will complete the ground paths for cooling fan relays Cool Fan #1, Cool Fan #2 Relay and Cool Fan #3 under any of the following conditions:
^ When engine coolant temperature exceeds 110°C (230°F).
^ When A/C refrigerant pressure is greater than 240 psi (2.5 volts).
^ When engine coolant temperature exceeds 108°C (226°F).
^ When A/C refrigerant pressure is greater than 240 psi (2.5 volts).