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.
Diesel Engine
Radiator fan operation is controlled by the Engine Control Module (ECM) with inputs from the temperature of the coolant, which is sensed by the coolant temperature sensor, and vehicle speed which is measured by the vehicle speed sensor. The ECM turns on the fan through either the high or low speed fan relay. The ECM provides a ground to the relay's control circuit. The fan relays are located on the back of the fan shroud.
If the cooling fan is inoperative or a Diagnostic Trouble Code (DTC) related to fan control has been set, for diagnostic procedures. Refer to appropriate engine powertrain control diagnostic information. .
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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.