The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the engine control module (ECM) or powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans receive positive voltage from the cooling fan relays which receive battery positive voltage from the underhood fuse block.

During low speed operation, the ECM or PCM supplies the ground path for the low speed fan relay, which is fan 1, relay through the low speed cooling fan relay control circuit. This energizes the fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the series/parallel relays, which is fan 2 relay, and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the ECM or PCM supplies the ground path for the fan 1 relay through the low speed cooling fan relay control circuit. The ECM or PCM grounds the high speed fan relay, which is fan 3 relay, and the fan 2 relay through the high speed cooling fan relay control circuit. This energizes the fan 2 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the fan 3 relay coil is energized closing the relay contacts and provides battery positive voltage from the fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.

When the requests for fan activation is withdrawn, the fan may not turn OFF until the ignition switch is moved to the OFF position or the vehicle speed exceeds approximately 10 mph. This is to prevent a fan from cycling ON and OFF excessively at idle.