For 1990-2009 cars only
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit/System Description
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.
Reference Information
Schematic Reference
Description and Operation
Cooling System Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Verify that DTCs P0480 and P0481 are not set.
- Ignition ON, verify with a scan tool that the ECM is not commanding the fan ON.
- Ignition ON, observe that the fan is not ON.
| ⇒ | If a DTCs is set, refer to DTC P0480 or P0481. |
Circuit/System Testing
- Ignition OFF, disconnect the appropriate cooling fan relay.
- Ignition ON, verify that the cooling fan is not ON.
- If all circuits test normal, test or replace the cooling fan relay.
| ⇒ | If the fan is ON, test for a short to voltage in the relay controlled output circuit terminal 87. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
