P0480

DTC P0480 or P0481

Circuit Description

Battery positive voltage is supplied to the cooling fan 1 relay from the COOL FAN #1 fuse. The powertrain control module (PCM) or engine control module (ECM) controls the cooling fan 1 relay by grounding the low speed cooling fan relay control circuit via an internal solid state device called a driver.

Battery positive voltage is supplied to the cooling fan S/P relay and the cooling fan 3 relay from the COOL FAN #2 fuse. The PCM/ECM controls the relays by grounding the high speed cooling fan relay control circuit.

When the PCM/ECM is commanding a relay ON, the voltage potential of the control circuit should be low, near 0 volts. When the PCM/ECM is commanding the control circuit to a relay, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the DTC will set.

The PCM/ECM will monitor the control circuit for the following:

* A short to ground
* A short to voltage
* An open circuit
* An open relay coil
* An internally shorted or excessively low resistance relay coil

When the PCM/ECM detects any of the above conditions, the DTC will set and the affected driver will be disabled.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

* DTC P0480 Cooling Fan 1 Relay Control Circuit
* DTC P0481 Cooling Fan 2 and 3 or S/P Relay Control Circuit

Conditions for Running the DTC

* The ignition is ON.
* 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

* The PCM/ECM detects an open, a short to ground, or a short to voltage on the cooling fan relay control circuit.
* The above conditions are present for at least 30 seconds.

Action Taken When the DTC Sets

* The PCM/ECM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
* The PCM/ECM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

Conditions for Clearing the MIL/DTC

* The PCM/ECM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.
* The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
* The DTC can be cleared by using the scan tool.

Diagnostic Aids

* If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Diagnostic Aids. Component Tests and General Diagnostics
* Review the Freeze Frame/Failure Records vehicle mileage since the diagnostic test last failed. This may help determine how often the condition that caused the DTC to be set occurs.

Test Description

The numbers below refer to the step numbers on the diagnostic table.
2. Listen for an audible click when the cooling fan 1 relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
3. Listen for an audible click when the cooling fan 3 or S/P relays operate. Command both the ON and OFF states. Repeat the commands as necessary.
4. This step tests for voltage at the coil side of the cooling fan 1 relay. The COOL FAN #1 fuse supplies battery positive voltage to the coil side of the cooling fan 1 relay.

Step 1 - Step 9:

Step 10 - Step 19:

Step 20 - Step 21: