The engine cooling fan is a two-speed electric fan. It is electronically controlled by the Powertrain Control Module (PCM), which monitors input from the engine coolant temperature (ECT) sensor, located in the intake manifold water outlet. The PCM sends signals to the fan control relays to operate the fan. There is one low speed and two high speed fan control relays. High speed fan control relay 2 is a safety relay. If high speed fan control relay 1 fails, relay 2 ensures cooling fan operation. If the ECT sensor fails, both high speed fan control relays activate the cooling fan whenever the ignition switch is on. The cooling fan should run at high speed whenever the A/C is on, regardless of engine temperature.