Purpose
The electric cooling fans are used to lower the temperature of the engine coolant flowing through the radiator. They are also used to cool the refrigerant (R134a) flowing through the A/C condenser.
Operation
Power for the fan motors is supplied through Cool Fan 1 Maxifuse® and Cool Fan 2 Maxifuse®. The cooling fan relays are energized when current flows from the fuses in the Underhood Electrical Center and through the relay coils to ground through the PCM. The Low Speed fans control circuit is grounded for low speed fans operation. The Cool Fan 1 relay control circuit and the Cool Fan 2 and Cool Fan 3 circuits are all grounded for high speed fans operation.
During low speed fans operation the PCM supplies a ground path for the Cool fan 1 relay. This closes the Cool Fan 1 relay contacts, allowing current to flow from the 40 amp Cool Fan 1 Maxifuse® through the relay contacts to the Engine Coolant Fan Motor #1. During low speed operation, the ground path for Engine Coolant Fan Motor #1 is through the Cool Fan 2 relay and the Engine Coolant Fan Motor #1. The result is a series circuit with both cooling fans running at low speed.
During high speed cooling fan operation the PCM supplies a ground path for the Cool Fan 1 relay. The PCM also supplies a ground path for Cool Fan 2 and Cool Fan 3 relay. This closes all three cooling fan relays. Engine Coolant Fan Motor #1 continues to receive current from the 40 amp Cool Fan 1 fuse. However, Engine Coolant Fan Motor #2 receives current from the 30 amp Cool Fan 2 fuse. During high speed operation each cooling fan has its own ground path.
The PCM will complete the ground path for low speed cooling fan relay under any of the following conditions:
| • | When engine coolant temperature exceeds 108°C (226°F). |
| • | When A/C is requested and ambient temperature is above 36°C (97°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 (140°F). |
The PCM will complete the ground paths for all engine three cooling fan relays under any of the following conditions:
| • | When engine coolant temperature exceeds 113°C (235°F). |
| • | When A/C refrigerant pressure is greater than 240 psi (2.5 volts). |
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.
Diagnosis
If a problem that involves the low speed cooling fan relay control circuit (cooling fan relay #1 control) exists, DTC P1651 should set. If the problem affects the high speed cooling fan relay control circuit (cooling fan relay #2 and #3 control), DTC P1652 should set. A problem with the ECT sensor should set DTC P0117, P0118, P1114, or P1115. Any of these DTCs will affect cooling fan operation and should be diagnosed before using the Electric Cooling Fan Diagnosis table. The Electric Cooling Fan Diagnosis table should be used to diagnose the PCM controlled cooling fans only if no DTC is set.
