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

In low speed operation, the ECM applies ground to the coil side of the low speed fan auxiliary relay. This energizes the coil and applies voltage directly to the auxiliary cooling fan through the switch side of the low auxiliary relay. The fan is connected in series to the main cooling fan through the de-energized S/P fan control relay. The series circuit operates both fans at low speed.

In high speed operation, the ECM applies a ground to the coil side of the fan auiliary relay, the S/P fan control relay, and the high speed fan Main relay. When energized, the fan main relay applies voltage directly to the main cooling fan through the switch side of the relay. Simultaneously, the fan auxiliary relay and the fan control relay provide ignition voltage and a direct path to ground for the auxiliary cooling fan. With both fans connected in a parallel circuit, each fan receives full voltage and operates at high speed.

The cooling fan will always operate anytime the A/C system is operating. First at low speed, and then at high speed when engine coolant temperature exceeds a specified value.