Operation
The engine coolant fan 1 receives power from a 40 amp maxifuse. The engine coolant fan 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 the primary cooling fan. The ground path for the primary cooling fan is through the series/parallel cooling fan relay (cool fan 2 relay) and secondary cooling fan 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 second 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 primary and the secondary cooling fans are supplied current from through the respective maxifuse and each fan has a ground.
Important: When certain 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 the engine coolant temperature exceeds 106°C (223°F). |
| • | When the A/C is requested and the ambient temperature is more than 50°C (122°F). |
| • | When the A/C refrigerant pressure is more than 190 psi (2 volts). |
| • | When the ignition is off and the engine coolant temperature is more than 140°C (284°F). |
For high speed cooling fan 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 the cooling fan relays under any of the following conditions:
| • | When the engine coolant temperature exceeds 110°C (230°F). |
| • | When the A/C refrigerant pressure is more than 240 psi (2.5 volts). |
Diagnosis
If a problem that involves the low speed cooling fan relay control circuit (cooling fan 1 relay control) exists, a DTC P1651 should set. If the problem affects the high speed cooling fan relay control circuit (cool fan 2 and cool fan 3 relay control), a DTC P1652 should set. A problem with the ECT sensor should set a 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.
