DTC P0480 or P0481 5.3 (LS4)

Diagnostic Instructions

DTC Descriptors

DTC P0480: Cooling Fan Relay 1 Control Circuit

DTC P0481: Cooling Fan Relay 2 and 3 Control Circuit

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Cooling Fan Relay 1 Control Circuit for the Fan 1 Relay	P0480	P0480	P0480	--
FAN 1 Relay Coil Voltage Supply Circuit	P0480	P0480	P0480	--
Cooling Fan Relay 2 and 3 Control Circuit for the Fan 2 and FAN 3 Relays	P0481	P0481	P0481	--
FAN 2 and FAN 3 Relays Coil Voltage Supply Circuit	P0481	P0481	P0481	--

Circuit/System Description

The engine control module (ECM) commands the fans ON in high speed or low speed. In low speed, the fans are configured in series. In high speed, the fans are configured in parallel.

In low speed operation, the ECM applies ground to the coil side of the low speed relay. Voltage is applied directly to the left cooling fan through the switch side of the low speed relay. The right fan is connected in series to the left fan through the de-energized series/parallel relay, which is the FAN 2 relay, so that both fans operate at low speed.

In high speed operation, the ECM applies a ground to the coil side of the low speed relay, the series/parallel relay, and the high speed relay. Voltage is applied directly to the right cooling fan through the switch side of the high speed relay. The left cooling fan obtains voltage through the low speed relay and ground through the series/parallel relay.

When the ECM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding a fan relay OFF, the voltage of the control circuit should be high, near battery voltage. If the ECM detects that the actual voltage of the relay control circuit is different than the expected voltage, DTC P0480 or P0481 will set and the affected ECM driver will be disabled.

Conditions for Running the DTC

Conditions for Setting the DTC

Action Taken When the DTC Sets

DTCs P0480 and P0481 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0480 and P0481 are Type B DTCs.

Reference Information

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

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

Circuit/System Verification

Verify cooling fan operation using the scan tool commands listed below:

Circuit/System Testing

1. Ignition OFF, disconnect the 3 cooling fan relays listed below.

•	FAN 1 relay

•	FAN 2 relay

•	FAN 3 relay

2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 85 of each relay and ground.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

3. Verify that a test lamp does not illuminate between the ignition circuit terminal 85 and the control circuit terminal 86 of each relay.

⇒	If the test lamp illuminates, test the control circuit for a short to ground. If the circuit test normal, replace the ECM.

4. Remove the test lamp.
5. Ignition ON, command the affected relay ON using a scan tool. Verify the affected scan tool FC Relay Control Ckt. Short Volts Test Status Parameter is OK.

•	For the FAN LO relay, use the scan tool Fan Relay 1 command.

•	For the FAN CNTRL and FAN HI relays, use the scan tool Relay 2 and 3 command.

⇒	If not the specified value, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.

6. Install a 3A fused jumper wire between the control circuit terminal 86 and the ignition circuit terminal 85. Command the affected relay ON with a scan tool. Verify the scan tool Relay Control Ckt Short Volts Test Status Parameter is Fault.

⇒	If not the specified value, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

7. If all circuits and the ECM test normal, replace the affected relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

DTC P0480 or P0481 3.8 - L26

Diagnostic Instructions

DTC Descriptors

DTC P0480: Cooling Fan Relay 1 Control Circuit

DTC P0481: Cooling Fan Relay 2 Control Circuit

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Low Speed Cooling Fan Relay Control Circuit for Fan 1 Relay	P0480	P0480	P0480	--
Fan 1 Relay Coil Voltage Supply Circuit	P0480	P0480	P0480	--
High Speed Cooling Fan Relay Control Circuit for Fan 3 Relay	P0481	--	P0481	--
Fan 3 Relay Coil Voltage Supply Circuit	P0481	P0481	P0481	--
High Speed Cooling Fan Relay Control Circuit for Fan 2 Relay	P0481	--	P0481	--
Fan 2 Relay Coil Voltage Supply Circuit	P0481	P0481	P0481	--

Circuit/System Description

The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans receive positive voltage from the cooling fan relays which receive battery positive voltage from the underhood fuse block.

During low speed operation, the PCM supplies the ground path for the low speed fan relay, which is fan 1 relay 42, through the low speed cooling fan relay control circuit. This energizes the fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the fan 1 fuse 29 through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the series/parallel relay, which is fan 2 relay 46, and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. The PCM grounds the high speed fan relay, which is fan 3 relay 43, and the series/parallel relay through the high speed cooling fan relay control circuit. This energizes the series/parallel relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the high speed fan relay coil is energized closing the relay contacts and provides battery positive voltage from the fan 2 fuse 32 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.

Conditions for Running the DTC

Conditions for Setting the DTC

Action Taken When the DTC Sets

DTCs P0480 and P0481 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0480 and P0481 are Type B DTCs.

Reference Information

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

Circuit/System Verification

1. Verify with a scan tool that the PCM is not commanding fan relay activation.
2. 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.
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition OFF, disconnect the series/parallel relay, which is fan 2 relay 46.
2. Connect a 30A fused jumper between the normally-open switch contact terminals M15 and K14 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 C18 for fan 1 relay or M18 for fan 3 relay.
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 at the affected relay connector and verify fan activation A18 for fan 1 relay or K18 for fan 3 relay.

⇒	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 terminal and the fan voltage supply circuit terminal at the affected relay connector and verify fan activation A18 and C19 for fan 1 relay or K18 and M19 for fan 3 relay.

⇒	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 and ground A19 for fan 1 relay or K19 for fan 3 relay.

⇒	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.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.