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.
Circuit Description
A/C clutch relay control circuit is controlled by an internal switch (driver) inside PCM. Driver incorporates a fault line that is monitored by PCM. When PCM commands relay on, voltage on control circuit is low (near zero volts). With relay commanded off, control circuit voltage reaches near battery voltage. If fault detection circuit senses a voltage other than what the expected voltage should be, DTC P0645 will set.
For duplication of DTC, ensure engine speed is greater than 400 RPM, and ignition voltage is 6-18 volts.
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.