P0480
DTC P0480 or P0481Circuit Description
^ DTC P0480 low speed cooling fan relay control circuit
^ DTC P0481 high speed cooling fan relay control circuit
Battery positive voltage is supplied to the fan 1 relay from the FAN 1 fuse. The Powertrain Control Module (PCM) controls the fan 1 relay by grounding the low speed cooling fan relay control circuit through an internal solid state device called a driver.
Battery positive voltage is supplied to the fan 2 relay and the fan relay from the FAN 2 fuse. The PCM controls the relays by grounding the high speed cooling fan relay control circuit.
When the PCM is commanding a relay on, the voltage potential of the control circuit should be low, near 0 volts. When the PCM 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 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 detects any of the above conditions, the DTC will set and the affected driver will be disabled.
Conditions for Running the DTC
^ System voltage is between 11-18 volts.
^ The relay control circuit is transitioned ON for at least.5 seconds.
Conditions for Setting the DTC
^ The PCM detects an open, or a short to ground on the cooling fan relay control circuit.
^ A short to voltage on the cooling fan relay control circuit will set the DTC instantly.
Action Taken When the DTC Sets
^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
^ The PCM 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 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 and Poor Connections.
^ Review the Freeze/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 fan 1 relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
3. Listen for an audible click when the fan 2 and fan 3 relays operate. Command both the ON and OFF states. Repeat the commands as necessary.
4. Tests for voltage at the coil side of the fan 1 relay. The FAN 1 fuse supplies battery positive voltage to the coil side of the fan 1 relay.
Steps 1-10:
Steps 11-21:
