P0480
DTC P0480 or P0481
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (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 and 3 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 COOL/FAN 1 relay 28. 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 COOL/FAN SER/PAR relay 29, 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 COOL/FAN 2 relay 30. 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
* The engine is running.
* The system voltage is between 11-18 volts.
* The relay control circuit is transitioned from OFF to ON, or ON to OFF.
Conditions for Setting the DTC
* An improper voltage level has been detected on the cooling fan relay control circuit.
* The condition must be present for a minimum of 30 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 (Diagrams)
Connector End View Reference
* Component Connector End Views (Connector End Views By Name)
* Electrical Center Identification Views (Application and ID)
Description and Operation
Cooling Fan Description and Operation (Cooling Fan)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
Verify cooling fan operation using the scan tool commands listed below:
* Fan Relay 1 ON-Both fans run at low speed.
* Fan Relays 2 and 3 ON-The right fan runs at high speed, the left fan is OFF.
* Fan Relays 1, 2 and 3 ON-Both fans run at high speed.
Circuit/System Testing
1. Ignition OFF, disconnect the 3 cooling fan relays listed below.
* COOL/FAN 1
* COOL/FAN SER/PAR
* COOL/FAN 2
2. Ignition ON, verify that a test lamp illuminates between ground and the appropriate battery voltage circuit terminal listed below:
* Cool Fan 1 relay, terminal 86
* Cool Fan 2 relay, terminal 86
* COOL/FAN SER/PAR relay, terminal 85
• If the test lamp does not illuminate, test the battery voltage circuit for a short to ground or an open/high resistance.
3. Verify that a test lamp does not illuminate between terminal 85 and terminal 86 of each relay listed below:
* COOL/FAN 1
* COOL/FAN 2
• 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 COOL/FAN 1 relay, use the scan tool Fan Relay 1 command.
* For the COOL/FAN SER/PAR and COOL/FAN 2 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 terminal 86 and 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 (Verification Tests) after completing the diagnostic procedure.
* Underhood Electrical Center or Junction Block Replacement (Underhood Electrical Center or Junction Block Replacement)
* Relay Replacement (Relay Replacement (Within an Electrical Center))
* Cooling Fan and Shroud Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming