Circuit Description

WARNING: This page is about a different car, the 2002 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.

Battery positive voltage is supplied to the cooling fan s/p relay and the cooling fan 2 relay from the cool fan 2 fuse. The powertrain control module (PCM) controls the relays by grounding the cooling fan 2 relay control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component on, the voltage potential of the control circuit should be low (near 0 volts). When the PCM is commanding the control circuit to a component off, the voltage potential of the circuit should be high (near battery voltage). If the fault detection circuit senses a voltage other than what is expected, the DTC will set.

The PCM will monitor the control circuit for the following:

A short to ground
A short to voltage
An open circuit
When the PCM detects any of the above conditions, the DTC will set and the affected driver will be disabled.