DTC P0480: Cooling Fan Relay No. 1 Control Circuit: Description

Battery positive voltage is supplied to cooling fan No. 1 relay from cool fan fuse. Powertrain Control Module (PCM) controls cooling fan No. 1 relay by grounding low speed control circuit via an internal driver. The primary function of the driver is to supply ground for component being controlled. Each driver has a fault line which is monitored by the PCM. When PCM is commanding a component on, the voltage potential of control circuit should be low (near zero volts). When PCM is commanding control circuit to a component off, voltage potential of the circuit should be high (near battery voltage).

PCM will monitor control circuit for the following: Short to ground, short to voltage, open circuit, open relay coil and internally shorted or excessively low resistance in relay coil.