P0480
DTC P0480 or P0481 (with RPO LC3 or LH2)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provide an overview of each diagnostic category.
DTC Descriptor
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 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 relay 1. 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 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, which is relay 1, the series/parallel relay, and the high speed relay, which is relay 2. 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
* The ignition is ON.
* The system voltage is between 9-18 volts.
* The relay control circuit is transitioned from OFF to ON or ON to OFF.
Conditions for Setting the DTC
P0480
The ECM detects an open circuit in the low speed cooling fan relay control circuit.
P0481
* The ECM detects an open circuit in the high speed cooling fan relay control circuit.
* The above condition is present for 30 seconds.
Action Taken When the DTC Sets
* DTC P0480 is a Type B DTC.
* DTC P0481 is a Type B DTC.
Conditions for Clearing the DTC
* DTC P0480 is a Type B DTC.
* DTC P0481 is a Type B DTC.
Reference Information
Schematic Reference
* Engine Cooling Schematics
* Power Distribution Schematics
Connector End View Reference
* Engine Control Module Connector End Views for the 3.6L engine
* Engine Control Module Connector End Views for the 4.4L engine
* Engine Control Module Connector End Views for the 4.6L engine
* Electrical Center Identification Views
Description and Operation
* Engine Control Module Description for the 3.6L engine
* Engine Control Module Description for the 4.4L engine
* Engine Control Module Description for the 4.6L engine
* Cooling Fan Description and Operation
Electrical Information Reference
* Circuit Testing
* Connector Repairs
* Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs
* Probing Electrical Connectors
* Electrical Center Identification Views
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
* Scan Tool Output Controls
* Scan Tool Data List
* Scan Tool Data Definitions
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 S/P fan relay.
2. Connect a 30A fused jumper between the normally-open switch contact terminals R15 and R16 at the S/P fan 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 terminals listed below:
* Low speed fan relay terminal R42
* High speed fan relay terminal R22
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.
* Fan 1 relay commands the low speed fan relay
* Fan 2 and 3 relays command the high speed fan relay
* 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 connectors listed below and verify fan activation.
* Low speed fan relay terminal R41
* High speed fan relay terminal R21
* 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 connectors listed below and verify fan activation.
* Low speed fan relay terminal R41
* High speed fan relay terminal R21
* 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 terminals listed below and ground.
* Low speed fan relay terminal R39
* High speed fan relay terminal R19
* 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
* Engine Cooling Fan Replacement (LH2 Heavy Duty Cooling) Engine Cooling Fan Replacement (LH2 Standard Cooling) Engine Cooling Fan Replacement (LY7)
* Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)
* Underhood Electrical Center or Junction Block Replacement
* Control Module References for ECM replacement, setup, and programming.