DTC P0480 or P0481 L26

The engine cooling fan system consists of 2 electrical cooling fans and three fan relays. The relays are arranged in a series/parallel (S/P) configuration that allows the powertrain control module (PCM) or engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block.

During low speed operation, the PCM supplies the ground path for the fan 1 relay 33, which is low speed fan relay, through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the fan 1 fuse 27 through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the fan 3 relay 32, which is series/parallel relay, and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation, the PCM or ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. The PCM supplies a ground path for the series/parallel and the fan 2 relay 31, which is high speed fan relay, through the high speed cooling fan relay control circuit. This energizes the high speed fan relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time, the series/parallel relay coil is energized closing the relay contacts, and provides battery positive voltage from the fan 2 fuse on the cooling fan motor supply voltage circuit, to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.

When the request for fan activation is withdrawn, the fan may not turn OFF until the ignition switch is moved to the OFF position or the vehicle speed exceeds approximately 10 mph. This is to prevent a fan from cycling ON and OFF excessively at idle.

DTCs P0480 and P0481 are Type B DTCs.

DTCs P0480 and P0481 are Type B DTCs.

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command each relay ON and OFF with a scan tool. Feel or listen to verify that each relay turns ON and OFF with each command.

1. Ignition OFF, disconnect the series/parallel relay, which is fan 3 relay 32.
2. Connect a 30A fused jumper between the normally-open switch contact terminals 30 and 87 at the series/parallel relay connector in order to complete the fan ground circuit. Leave this jumper in place for the remainder of this procedure.
3. Ignition OFF, disconnect the affected relay.
4. Ignition ON, connect a test lamp between the positive terminal at the battery and the affected relay control circuit terminal 85 for fan 1 relay 33, or terminal 86 for fan 3 relay 31.
5. Command the affected relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the relay control circuit for a short to ground. If the circuit tests normal, replace the PCM.

⇒	If the test lamp is always OFF, test the relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the PCM.

6. Connect a 30A fused jumper between the positive voltage terminal at the battery and the fan voltage supply circuit terminal 85 for fan 1 relay 33, and terminal 86 for fan 3 relay 31 connector 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, replace the fan.

7. Ignition ON, connect a 30A fused jumper between the relay switch voltage supply circuit and the fan voltage supply circuit terminals 86 and 87 for fan 1 relay 33, and terminals 85 and 87 for fan 2 relay 31 at the affected relay connector and verify fan activation.

⇒	If the fan does not activate, test the affected relay switch voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, test all connected components and replace as necessary.

8. Ignition ON, verify that a test lamp illuminates between the affected relay coil voltage supply circuit terminal 30 and ground.

⇒	If the test lamp does not illuminate, test the affected relay coil voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, test all connected components and replace as necessary.

9. If all circuits and the PCM test normal, replace the affected relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.