Radiator Fan Relay Control Circuit

WHEN MONITORED
With the ignition key on and battery voltage greater than 10 volts.

SET CONDITION
An open or shorted condition is detected in the radiator fan relay control circuit.

THEORY OF OPERATION
The radiator fan relay controls the operation of the radiator fan.

- One side of the relay control coil is supplied with 12 volts when the ignition switch is turned to the RUN position.

- The circuit is completed when the other side of the relay coil is grounded by the powertrain control module (PCM).

The PCM grounds the relay control circuit depending on coolant temperature.

- When the engine coolant temperature has reached the maximum temperature parameter, the relay will be grounded.

- Conversely, when the engine coolant temperature has acquired the minimum temperature parameter, the relay will remove the ground.

PROBABLE CAUSES
- Relay coil open or shorted
- Fused ignition switch output circuit open
- Low speed radiator fan relay control circuit open or shorted
- Inoperative circuit driver in PCM