Cooling Fan Control

WARNING: This page is about a different car, the 2010 Pontiac G5 and 2010 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.

The engine cooling fan system consists of one cooling fan and two relays. The cooling fan has 2 windings in the motor, one winding is for low speed and the other winding is for high speed. Voltage is supplied to the relays from the 30 A cooling fan 1 and 30 A cooling fan 2 fuses. The engine control module (ECM) controls the low speed fan operation by grounding the cool fan 1 relay control circuit. When the cooling fan 1 relay is energized, voltage is delivered to the cooling fan low speed winding. The ECM controls the high speed fan operation by grounding the cool fan 2 relay control circuit. When the cooling fan 2 relay is energized, voltage is delivered to the cooling fan high speed winding. The cooling fan motor is grounded through its own ground circuit.

The PCM commands Low Speed Fans ON under the following conditions:

Engine coolant temperature (ECT) exceeds approximately 106°C (223°F).
A/C refrigerant pressure exceeds 1 310 kPa (190 psi).
After the vehicle is shut off, the ECT at key-off is greater than 140°C (284°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.

The PCM commands High Speed Fans ON under the following conditions:

ECT reaches 110°C (230°F).
A/C refrigerant pressure exceeds 1 655 kPa (240 psi).
When certain DTCs set