DTC P0480 Or P0481: Cooling Fan Relay Control Circuit: Description

1. P0480 -  Low Speed Cooling Fan Relay Control Circuit
2. P0481 -  High Speed Cooling Fan Relay Control Circuit

Battery positive voltage is supplied to the cooling fan 1 relay from the COOL FAN #1 fuse. The Powertrain Control Module (PCM) 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 2 relay and the cooling fan 3 relay from the COOL FAN #2 fuse. The PCM controls the relays by grounding the high speed cooling fan relay control circuit.

When PCM is commanding a relay on, the voltage potential of the control circuit should be low, about zero 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.

PCM will monitor the control circuit for a short to ground, short to voltage, open circuit, open relay coil, or an internally shorted or excessively low resistance relay coil. When PCM detects any of the conditions, DTC will set and the affected driver will be disabled.