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
The PCM monitors certain parameters (such as engine coolant temperature, vehicle speed, A/C on/off status, A/C pressure) to determine engine cooling fan needs.
The PCM controls the fan speed and operation using a duty cycle output on the fan control variable (FCV) circuit. The fan controller (located at or integral to the engine cooling fan assembly) receives the FCV command and operates the cooling fan at the speed requested (by varying the power applied to the fan motor).
FCV DUTY CYCLE OUTPUT FROM PCM (negative duty cycle)
| FCV Duty Cycle Command (NEGATIVE (-) duty cycle) | Cooling Fan Response/Speed |
|---|---|
| Greater than 0 but less than 5% | Fan off, controller inactive |
| Greater than 5% but less than 10% | Fan off, controller is in active/ready state |
| 30% - 90% | Linear speed increase from 50% to 100% |
| Greater than 90% but less than 95% | 100% |
| Greater than 95% but less than 100% | Fan off |
NO RELATED
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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.