The engine control module (ECM) controls cooling fan operation in either high speed or low speed mode, depending on cooling requirements. To activate a fan, the ECM applies ground to the coil side of the applicable fan relay. This energizes the coil and applies voltage directly to the cooling fan through the switch side of the relay.

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

Scan Tool Reference

1. Verify that DTCs P0480 and P0481 are not set.

⇒	If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

2. Ignition ON, verify with a scan tool that the ECM is not commanding the fan ON.

⇒	If the fan is commanded ON, refer to DTC P0480 or P0481 .

3. Ignition ON, observe that the fan is not ON.

Important: The following tests must be performed on each cooling fan relay.

1. Ignition OFF, disconnect each cooling fan relay one at a time.
2. Ignition ON, observe that the cooling fans are not ON.

⇒	If the fans are ON, test for a short to voltage in the relay controlled output circuit terminal 87.

⇒	If the fans are not ON, test for a short to ground in the relay coil control circuit terminal 86.

3. If all circuits test normal, test or replace the cooling fan relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Relay Replacement