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.
For Relay Controlled Fans
The PCM controls the fan operation through the fan control LFC (single speed applications), and LFC (low speed), MFC (medium speed), HFC (high speed) for multiple speed applications. Some applications have the xFC circuit wired to 2 separate relays.
For 2 speed fans, although the PCM output circuits are called LFC and HFC, cooling fan speed is controlled by a combination of these outputs.
For 3 speed fans, although the PCM output circuits are called LFC, MFC, and HFC, cooling fan speed is controlled by a combination of these outputs.
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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.