Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Engine Cooling Fan Control
The PCM controls operation of the engine cooling fan based on coolant temperature, air conditioning state and vehicle speed. If the coolant rises above 223°F (106°C) or if the air conditioning compressor is turned on, the PCM will supply a ground to the engine coolant fan relay, energizing the relay and engine cooling fan. The PCM will shut off the cooling fan if the vehicle exceeds 70 MPH (97 KM/H) for three minutes.
When the PCM stops receiving an A/C request signal, it will run the cooling fan for one minute, then de-energize the relay, which will turn off the cooling fan. The A/C high or low pressure switches open the A/C request circuit from the A/C control head to the PCM. The cooling fan is turned on, after the initialization delay, when any of the following conditions are present: An ECT failure has been detected (DTCs P0117, P0118, P0125, P0217, P1114, P1115 and P1620).
When coolant temperature exceeds 230°F (110°C) or vehicle is turned OFF, and ECT temperature is 230°F (110°C) or greater, the cooling fan will be turned ON.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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