Operation
The engine cooling fans receive power from Fuse 6 40A and Fuse 21 15A located in the Underhood Accessory Wiring Junction Block. During low speed operation, the powertrain control module (PCM) supplies a path to ground for Relay 12 through the Low Speed Fans control circuit. This energizes the relay coil, closes Relay 12's contacts, and supplies current from Fuse 6 40A to the engine cooling fans. Engine Coolant Fan Motor (RH) grounds through the series/parallel cooling fan relay (Relay 9) and Engine Coolant Fan Motor (LH). This creates 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 Relay 12 through the Low Speed Fans Control circuit. After a 3 second delay, the PCM supplies a path for ground through Relay 9 and Relay 10 through the High Speed Fans Control circuit. Engine Coolant Fan Motor (RH) continues to receive current from Fuse 6 40A. However, Fuse 21 15A supplies current to Engine Coolant Fan Motor (LH). Each fan receives a separate path to ground. Therefore, the fans operate at high speed.
Important: When certain Diagnostic Trouble Codes (DTCs) set, the PCM may command the cooling fans to run all the time. Perform the Powertrain On-Board Diagnostic System Check. Refer to Powertrain On Board Diagnostic (OBD) System Check prior to diagnosing the engine cooling fans.
The PCM completes the ground path for Relay 12 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 operation, the PCM delays control of the Engine Coolant Fan Motor (LH) and Relay 10 for 3 seconds. The 3 second delay ensures that cooling fan electrical load does not exceed the capacity of the system. The PCM completes the ground paths for Relay #12, Relay 9 and Relay 10 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). |
Diagnosis
DTC P1651 may set if a problem occurs which affects the low speed fans control circuit. If the problem affects the high speed fans control circuit, DTC P1652 may set. A problem with the engine coolant temperature (ECT) sensor may set DTC P0117, P0118, P1114, or P1115. Any of these DTCs will affect cooling fan operation. Therefore, diagnose any PCM DTCs before using the Electric Cooling Fan Diagnosis table. If DTCs are not set and a cooling fan problem exists, refer to Electric Cooling Fan Diagnosis to diagnose the PCM controlled cooling fans.
