Cooling Fan Inoperative

Cooling Fan Inoperative

Circuit/System Description

The engine control module (ECM) grounds the cooling fan relay control circuits through an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line that is monitored by the ECM. When the ECM is commanding a component ON, the voltage potential of the control circuit should be low, near 0 volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be high, near battery voltage. If the ECM detects that the actual state of the control circuit does not match the expected state, a DTC will set.

Reference Information

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

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

Circuit/System Verification

1. If DTCs P0480 or P0481 are set, then perform those diagnostics first.
2. Ignition ON, command each relay ON and OFF with a scan tool. Observe to verify that the fan turns ON and OFF with each command.

Circuit/System Testing

1. Ignition OFF, disconnect the relay.
2. Ignition OFF, connect a 30A fused jumper between the positive terminal at the battery and the fan voltage supply circuit terminal, and verify fan activation.

^ If the fan does not activate, test the fan voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, test the fan ground circuit for an open/high resistance. If the fan does not activate and the circuits test normal, replace the fan.

3. Ignition ON, connect a 30A fused jumper from the relay switch voltage supply circuit terminal to the fan voltage supply circuit terminal and verify fan activation.

^ If the fan does not activate, test the relay switch voltage supply circuit for a short to ground or an open/high resistance.

4. If all circuits test normal then replace the faulty relay.

Repair Verification

Ignition ON, command the relay ON and OFF with a scan tool. Observe to verify that the fan turns ON and OFF with each command.