GM Service Manual Online
For 1990-2009 cars only

DTC P0480 or P0481 5.3 (LS4)

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    •  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 and 3 Control Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Cooling Fan Relay 1 Control Circuit for the Fan 1 Relay

P0480

P0480

P0480

--

FAN 1 Relay Coil Voltage Supply Circuit

P0480

P0480

P0480

--

Cooling Fan Relay 2 and 3 Control Circuit for the Fan 2 and FAN 3 Relays

P0481

P0481

P0481

--

FAN 2 and FAN 3 Relays Coil Voltage Supply Circuit

P0481

P0481

P0481

--

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. 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 FAN 2 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, the series/parallel relay, and the high speed relay. 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

    • 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

Connector End View Reference

    •  Component Connector End Views
    •  Powertrain Component Views
    •  Electrical Center Identification 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

Control Module References

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.
  2. • FAN 1 relay
    • FAN 2 relay
    • FAN 3 relay
  3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 85 of each relay and ground.
  4. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  5. Verify that a test lamp does not illuminate between the ignition circuit terminal 85 and the control circuit terminal 86 of each relay.
  6. If the test lamp illuminates, test the control circuit for a short to ground. If the circuit test normal, replace the ECM.
  7. Remove the test lamp.
  8. 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.
  9. • For the FAN LO relay, use the scan tool Fan Relay 1 command.
    • For the FAN CNTRL and FAN HI 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.
  10. 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.
  11. If not the specified value, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  12. If all circuits and the ECM test normal, replace the affected relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement
    •  Underhood Electrical Center or Junction Block Replacement
    •  Control Module References for ECM replacement, setup, and programming