P0480

DTC P0480 or P0481

Circuit Description

The Cooling Fan Relay 1 or RAD FAN LOW relay, and Cooling Fan Relay 2 or RAD FAN HI relay are controlled by the engine control module (ECM). Battery positive voltage is supplied to the relay coil. The ECM monitors the voltage level on the control circuit of the relay. When the relay is off, voltage level should be near battery voltage on the control circuit of the relay. When the relay is commanded on, voltage level will be low on the control circuit of the relay. The ECM will provide ground on the control circuit of the relay using a low side driver. If the ECM detects a improper voltage level on the control circuit of the relay, a DTC will set.

DTC Descriptor

This diagnostic procedure supports the following DTCs:

* DTC P0480 Cooling Fan Relay 1 Control Circuit
* DTC P0481 Cooling Fan Relay 2 Control Circuit

Conditions for Running the DTC

* The ignition is ON or the engine is operating.
* The ignition 1 voltage is more than 10 volts.
* DTCs P0480 and P0481 run continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM detects one of the following conditions on the control circuit of one of the relays:

* An open
* A short to ground
* A short to voltage

Action Taken When the DTC Sets

* The malfunction indicator lamp (MIL) will not illuminate.
* The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.

Conditions for Clearing the MIL/DTC

* DTCs can be cleared by using the scan tool.
* Disconnect the ECM battery feed for more than 10 seconds.

Diagnostic Aids

* For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections.
* The following tables illustrate the RAD FAN LOW relay and RAD FAN HIGH relay terminal locations in the underhood fuse block:










Test Description

The numbers below refer to the step numbers on the diagnostic table.
6. A test lamp that remains illuminated indicates a short to ground on the control circuit. A test lamp that does not illuminate indicates an open or short to voltage on the control circuit.
8. This step tests the control circuit for high resistance.