PWM Fan Control Module - 4.0L: Operation

The PWM relay is used to control the speed of the electric radiator cooling fan. It allows for multiple fan speeds. This allows for improved fan noise and A/C performance, better engine cooling, and additional vehicle power.

PWM relay operation is controlled by the Powertrain Control Module (PCM). To operate the PWM relay, the PCM looks at inputs from:

• Engine coolant temperature
• Ambient temperature from the body controller
• Vehicle speed
• Transmission oil temperature
• A/C switch position (A/C request)