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 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 FAN 1 relay 33. 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 3 relay 32, 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 FAN 2 relay 31. 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 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
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 (Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Engine Control Module Description (Engine Control Module Description)
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 Tools Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
Verify the 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:
* Fan 1 relay
* Fan 2 relay
* Fan 3 relay
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 85 of each relay and ground.
• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
3. Verify that a test lamp does not illuminate between the ignition circuit terminal 85 and the control circuit terminal 86 of each relay.
• 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 fan 1 relay, use the scan tool Fan Relay 1 command.
* For the fan 2 and fan 3 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 the control circuit terminal 86 and the ignition circuit 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
* Underhood Electrical Center or Junction Block Replacement (Removal and Replacement)
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Engine Coolant Fan Shroud Replacement (LGD, LZ9) (Service and Repair)Engine Coolant Fan Shroud Replacement (L37) (Service and Repair)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming
Repair 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.