P0481
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 low relay, which is relay 1. Voltage is applied directly to the left cooling fan through the switch side of the fan low relay, which is fed by the fan 1 fuse. The right fan is connected in series to the left fan through the de-energized fan control relay, which is the series/parallel relay, so that both operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the fan low relay, the fan control relay, and the fan high relay, which is relay 2. Voltage is applied directly to the right 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 low relay and ground through the fan control 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.
* The ignition is ON.
Conditions for Setting the DTC
* The commanded state of the 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
* Electrical Center Identification Views
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
* Scan Tool Data List
* Scan Tool Data Definitions
* Scan Tool Output Controls
Special Tools Required
J 43244 Relay Puller Pliers
Circuit/System Verification
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 series/parallel relay.
2. Connect a 30A fused jumper between the normally-open switch contact terminals 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.
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 ECM.
^ 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 ECM.
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.
^ 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.
^ 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 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 ECM test normal, replace the affected relay.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* Relay Replacement (Within an Electrical Center) Relay Replacement (Attached to Wire Harness)
* Underhood Electrical Center or Junction Block Replacement
* Control Module References for ECM replacement, setup, and programming