Cooling Fan Control

WARNING: This page is about a different car, the 2022 Cadillac CT5. However, it is still accessible from the selected car via links, so may be relevant.

The engine cooling fan system is composed of 1 electric cooling fan and an integral cooling fan control module. The cooling fan control module communicates with the engine control module (ECM) via a local interconnect network (LIN). The ECM controls the fan speed by sending a pulse width modulated (PWM) signal to the cooling fan control module over a serial data circuit or (LIN Buss). The cooling fan control module varies the voltage drop across the cooling fan motor in relation to the pulse width modulated signal, which allows the cooling fan to operate at variable speeds.

The cooling fan speed is effected by many different conditions and the ECM will adjust the duty cycle from 0 - 100 percent based on cooling system requirements. The actual commanded cooling fan speed is based on a number of inputs from the ECM, and cooling fan requests from other modules, such as the BCM, TCM, and HPCM, if equipped. When multiple cooling fan speed requests are received, the ECM operates the fan at the highest of speed requests. The scan tool output control is only capable of operating the cooling fan in increments, between 10 - 90 percent. 90 percent is considered high speed fan. The ECM commands the fans ON under the following conditions:

The engine coolant temperature is warmer than a predetermined value
The engine oil temperature is warmer than a predetermined value
The transmission fluid temperature is warmer than a predetermined value
The A/C pressure reaches a predetermined pressure.
If the engine coolant temperature at key-off is warmer than a predetermined value, or the A/C pressure is greater than a predetermined value, the cooling fan will operate at a low speed. The fan will shut OFF if the temperature or pressure drops below the predetermined value, but will only operate for 2 minutes, regardless of the coolant temperature or A/C pressure.