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.
Fan Control
PCM monitors certain parameters such as: engine coolant temperature, vehicle speed, A/C on/off status and A/C pressure to determine engine cooling fan needs. PCM controls fan operation through Fan Control (FC) on single speed fan applications, or Low Fan Control (LFC), Medium Fan Control (MFC) and/or High Fan Control (HFC) outputs on 3 speed fan applications. Although PCM output circuits for 3-speed fans are called low, medium and high fan control, cooling fan speed is controlled by a combination of these outputs. See Fig 1.
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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.