P0480

DTC P0480 or P0481
Circuit Description
The powertrain control module (PCM) or engine control module (ECM) controls the low speed cooling fan operation by grounding the low speed fan relay control circuit with an internal solid state device called a driver. For high speed cooling fan operation, the PCM or ECM grounds the high speed and S/P relay control circuit at the same time the low speed control circuit is grounded. Battery positive voltage is supplied to the low speed, high speed and S/P fan relays. When the PCM or ECM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the PCM or ECM is commanding a fan relay OFF, the voltage potential of the control circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the DTC will set.

If the PCM or ECM detects an improper voltage level on the low or high speed driver circuits, then code P0480 or P0481 will set and the affected driver will be disabled.

DTC Descriptors
This diagnostic procedure supports the following DTC's:
^ DTC P0480 Cooling Fan Relay 1 Control Circuit
^ DTC P0481 Cooling Fan Relay 2 and 3 Control Circuit

Conditions for Running the DTC
^ The ignition voltage is between 9 - 18 volts.
^ The engine speed is more than 40 RPM.
^ The PCM or ECM driver transitions from ON to OFF or from OFF to ON.

Action Taken When the DTC Sets
^ The PCM or 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 or ECM records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
^ The PCM or ECM stores the DTC information into memory when the diagnostic runs and fails.
^ The driver information center (DIC) if equipped, may display a message.

Conditions for Clearing the MIL/DTC
^ The PCM or ECM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.
^ A current DTC last test failed clears when the diagnostic runs and passes.
^ Use the scan tool in order to clear the MIL and the DTC.

Diagnostic Aids
^ If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections. Component Tests and General Diagnostics
^ Review the Freeze/Failure Records vehicle mileage since the diagnostic test 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 cool fan relay 1 operates. Command both the ON and OFF states. Repeat the commands, as necessary.
3. Listen for an audible click when the S/P and cool fan 2 relays operate. Command both the ON and OFF states. Repeat the commands, as necessary.

Step 1 - Step 11:

Step 12 - Step 21: