Cooling Fan Always On. Chevrolet Joy 2008

For 1990-2009 cars

### 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

Engine Cooling Schematics

#### Connector End View Reference

• | Cooling System Component Views

• | Cooling System Connector End Views

#### Description and Operation

Cooling Fan Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

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.

### Circuit/System Testing

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.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Relay Replacement