DTC P0480 or P0481 Except LAT

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 AUX Fan Relay 12	P0480	P0480	P0480	--
Coil Voltage Supply Circuit for AUX Fan Relay 12	P0480	P0480	P0480	--
High Speed Cooling Fan Relay Control Circuit for Main Fan Relay 16	P0481	P0481	P0481	--
Coil Voltage Supply Circuit for Main Fan Relay 16	P0481	--	P0481	--
High Speed Cooling Fan Relay Control Circuit for Fan Control Relay 15	P0481	P0481	P0481	--
Coil Voltage Supply Circuit for Fan Control Relay 15	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, which is the auxiliary fan relay 12. 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 fan control relay 15, 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, which is the main fan relay 16. 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.

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 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 ECM 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 control relay 15.
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. Verify that a test lamp does not illuminate between B+ and the affected relay control circuit terminal 86.
5. Remove the test lamp.
6. Command the affected relay ON with a scan tool. Verify the scan tool Relay Control Ckt. Short Volts Test Status Parameter is OK.

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

7. Install a 3A fused jumper wire between the control circuit terminal 86 and B+. 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.

8. Remove the 3A fused jumper wire.
9. Connect a 30A fused jumper between the positive voltage terminal at the battery and the fan voltage supply circuit terminal 87 at the affected relay 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.

10. Ignition ON, connect a 30A fused jumper between the relay switch voltage supply circuit terminal 30 and the fan voltage supply circuit terminal 87 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.

11. Ignition ON, verify that a test lamp illuminates between the affected relay coil voltage supply circuit terminal 85 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.

12. 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 LAT

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	P0480	P0480	P0480	--
Low Speed Cooling Fan Relay Coil Voltage Supply Circuit	P0480	P0480	P0480	--
High Speed Cooling Fan Relay Control Circuit	P0481	P0481	P0481	--
High Speed Cooling Fan Relay Coil Voltage Supply Circuit	P0481	P0481	P0481	--

Circuit/System Description

The engine control module (ECM) grounds the low speed relay, which is the AUX fan relay, and the high speed relay, which is the main 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.

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 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. Ignition ON, verify with a scan tool that the ECM 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.

Circuit/System Testing

1. Ignition OFF, disconnect the affected relay.
2. Verify that a test lamp does not illuminate between B+ and the affected relay control circuit terminal 86.

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

3. Remove the test lamp.
4. Command the affected relay ON with a scan tool. Verify the scan tool Relay Control Ckt. Short Volts Test Status Parameter is OK.

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

5. Install a 3A fused jumper wire between the control circuit terminal 86 and B+. 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.

6. Remove the 3A fused jumper wire.
7. Connect a 30A fused jumper wire between the positive voltage terminal at the battery and the fan voltage supply circuit terminal 87 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.

8. Ignition ON, connect a 30A fused jumper wire between the relay switch voltage supply circuit terminal 30 and the fan voltage supply circuit terminal 87 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. If the circuit tests normal and its fuse is open, replace the relay.

9. Ignition ON, verify that a test lamp illuminates between the relay coil voltage supply circuit terminal 85 and ground.

⇒	If the test lamp does not illuminate, test the 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, replace the relay.

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.