Test Description
- P0480 is for the low speed cooling fan relay control circuit.
- P0481 is for the high speed cooling fan relay control circuit.
Battery positive voltage is supplied to the cool fan 1 relay from the COOL FAN 1 fuse. The powertrain control module (PCM) controls the cool 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 cool fan 2 relay and the cool fan relay from the COOL FAN 2 fuse. The powertrain control module (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.
The numbers below refer to the step numbers on the diagnostic table.
- 2. Listen for an audible click when the cool fan 1 relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
- 3. Listen for an audible click when the cool fan 2 and cool fan relays operate. Command both the ON and OFF states. Repeat the commands as necessary.
- 4. Tests for voltage at the coil side of the cool fan 1 relay. The COOL FAN 1 fuse supplies battery positive voltage to the coil side of the cool fan 1 relay.