P0480
DTC P0480 or P0481
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P0480
- Cooling Fan Relay 1 Control Circuit
DTC P0481
- Cooling Fan Relay 2 Control Circuit
Diagnostic Fault Information
Circuit/System Description
The engine control module (ECM) commands the fans ON in either high speed or low speed, depending on cooling requirements. 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 fan 1 relay. Voltage is applied directly to the right cooling fan through the switch side of the fan 1 relay, which is fed by the fan 1 fuse. The left fan is connected in series to the left fan through the de-energized fan 2 relay so that both operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the fan 1 relay, the fan 2 relay, and the fan 3 relay. Voltage is applied directly to the left cooling fan through the switch side of the relay, which is fed by the fan 2 fuse. The left cooling fan obtains voltage through the fan 1 relay and ground through the fan 2 relay.
The ECM monitors the low and high speed cooling fan relay control circuits for the following conditions:
* Short to ground
* Short to voltage
* An open circuit
If the ECM detects an improper voltage level on the low or high speed ECM driver circuits, then DTC P0480 or P0481 will set and the affected ECM driver will be disabled.
Conditions for Running the DTC
The battery voltage is between 9-18 volts.
Conditions for Setting the DTC
* The commanded state of the output driver module (ODM) and the actual state of the control circuit do not match.
* The condition is present for more than 5 seconds.
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
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
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Scan Tool Data List
Circuit/System Verification
1. Ignition ON, command the cooling fan relay 1 ON and OFF several times using the scan tool output control function. You should hear both fans turn ON and OFF. Both should run on low speed when turned ON.
2. Command the cooling fan relays 2 and 3 ON and OFF several times using the scan tool output control function. When turned ON, the right fan should run on high and the left fan should remain OFF.
3. Command the cooling fan relays 1, 2, and 3 ON and OFF several times using the scan tool output control function. When turned ON, both fans should run on high speed.
Circuit/System Testing
P0480
1. Ignition OFF, disconnect the fan 1 relay from the underhood fuse block.
2. Ignition ON, verify that a test lamp illuminates between the fan 1 relay coil voltage supply circuit and ground.
^ If the test lamp does not illuminate, test the fan 1 relay coil voltage supply circuit for and open/high resistance.
3. Connect a test lamp between the fan 1 relay coil supply voltage circuit and the fan 1 relay coil control circuit. With a scan tool, command the fan relay 1 ON and OFF. Verify that the test lamp turns ON and OFF with each command.
^ If the test lamp remains illuminated with each command, test the fan 1 relay control circuit for a short to ground. If the circuit tests normal, replace the ECM.
^ If the test lamp does not illuminate, test the relay coil control circuit for and open or a short to voltage. If the circuit tests normal, replace the ECM.
4. If the circuits test normal, replace the fan 1 relay.
P0481
1. Ignition OFF, disconnect the cooling fan 3 relay from the underhood fuse block.
2. Ignition ON, verify that a test lamp illuminates between the fan 3 relay coil voltage supply circuit and ground.
^ If the test lamp does not illuminate, test the fan 3 relay coil voltage supply circuit for and open/high resistance.
3. Connect a test lamp between the fan 3 relay coil supply voltage circuit and the fan 3 relay coil control circuit. With a scan tool, command the fan relays 2 and 3 ON and OFF. Verify that the test lamp turns ON and OFF with each command.
^ If the test lamp remains illuminated with each command, remove the fan 2 relay and retest. If the test lamp now turns ON and OFF with the fan 2 relay removed, replace the fan 2 relay. If the test lamp still remains illuminated when commanded ON and OFF, test the fan 3 relay coil control circuit for a short to ground. If the circuit tests normal, replace the control module.
^ If the test lamp does not illuminate, test the fan 3 relay control circuit for and open or a short to voltage. If the circuit tests normal, replace the control module.
4. If all circuits test normal, replace the fan 3 relay.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)
* Control Module References for ECM replacement, setup, and programming refer to programing and relearning Programming and Relearning