Cooling Fan Description and Operation

Cooling Fan Description and Operation

Cooling Fan Control 2.0L

The engine cooling fan is a variable speed fan. The engine control module (ECM) controls the fan speed by sending a pulse width modulated (PWM) signal to the cooling fan control module. The cooling fan control module varies the voltage drop across the engine cooling fan motor in relation to the PWM signal. The cooling fan speed can be adjusted from 10 percent to 94 percent duty cycle. 94 percent is considered high speed fan.

The ECM commands fans ON under the following conditions:

Fan Control During Engine Operation (Engine ON)

* Fixed 94 percent duty cycle commanded when the following conditions are met:
^ Engine oil temperature is greater than 140°C (284°F).
^ AT transmission temperature is greater than 140°C (284°F)
^ Intake air temperature is greater than 65°C (149°F).
^ Engine coolant temperature sensor faults have been detected (electrical or rational).
* Variable duty cycle from 15-95 percent is commanded when:
^ From all available requests, the maximum requested duty cycle is selected and commanded.
^ Dependant on engine coolant temperature, 0 percent up to 92.9°C (199.22°F). Then 15 percent at 93°C (199.4°F) to greater than 94 percent by 121°C (249.8°F).
^ Dependant on A/C pressure sensor, 0 percent up to 10,979 hPa. Then 15 percent at 10,980 hPa to greater than 94 percent by 23,529 hPa.
^ Fans commanded off during running operation when the above conditions are not met.

Fan Control During After-run (Engine OFF)
* Fixed 36 percent duty cycle commanded after shut-down when the engine coolant temperature at shut-down is greater 101°C (213°F).
* Fixed 60 percent duty cycle commanded after shut-down when the engine coolant temperature at shut-down is greater than 108°C (226.4°F).
* Fans commanded OFF during after-run when:
^ System voltage is less than 11.5 V
^ After-run time is greater than 420 seconds.
^ Coolant temperature drops below a variable threshold.

Cooling Fan Control 2.4L

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 through 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, which is the low speed relay, 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, which is the high speed 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 ECM 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 ECM 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

When the request for fan activation is withdrawn, the fan may not turn OFF until the ignition switch is moved to the OFF position or the vehicle speed exceeds approximately 10 mph. This is to prevent a fan from cycling ON and OFF excessively at idle.