P0480

DTC P0480 or P0481








Circuit Description

The following DTCs are tor the cooling fan relay control circuits controlled by the powertrain control module (PCM).

- P0480 low speed cooling tan relay control circuit

- P0481 - high speed cooling tan relay control circuit

Battery positive voltage is supplied to the COOL FAN 1 Relay from the COOL FAN 1 Fuse. The PCM controls the low speed cooling fan relay by grounding the low speed cooling fan relay control circuit.

Battery positive voltage is supplied to the COOL FAN 2 Relay and the COOL FAN 3 Relay from the COOL FAN 2 Fuse. The PCM controls the high speed cooling fan relays by grounding the high speed cooling fan relay control circuit.

The PCM grounds the cooling fan relay control circuits through an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line that is monitored by the PCM. When the PCM is commanding a component on, the voltage potential of the control circuit should be low, near 0 volts. When the PCM is commanding the control circuit to a component off, 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 eftected driver will be disabled.


Conditions for Running the DTC

- The engine speed is more than 425 RPM.

- The system voltage is between 8.0 and 18.0 volts.


Conditions for Setting the DTC

- An improper voltage level has been detected on the cooling fan relay control circuit.

- The condition is present for at least 10 seconds.


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 the conditions that were present when the DTC set as Freeze Frame and Failure Records data.

- A history DTC is stored.


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 in Wiring Systems.

- 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 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 2 and the cooling 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 cooling fan 1 relay. The cool fan 1 fuse supplies battery positive voltage to the coil side of the cooling fan 1 relay.

5. Verifies that the PCM is providing ground to the cooling fan 1 relay.

6. Tests for voltage at the coil side of the cooling fan 2 relay. The cool fan 2 fuse supplies battery positive voltage to the coil side of the cooling fan 2 and cooling fan 3 relays.

7. Verifies that the PCM is providing ground to the cooling fan 2 relay.

8. Verifies that the PCM is providing ground to the cooling fan 3 relay.

9. Tests if ground is constantly being applied to the cooling fan relays.

10. Test the control circuit of the cooling fan relays for a short to voltage or an open.

11. Test the control circuit of the cooling fan relays for a short to ground.

12. Test the battery positive voltage circuit for a short to ground.