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
The DTC P0325 Knock Sensor (KS) Circuit diagnostic monitors activity on the knock sensor circuit. The KS is non-resonant design that is constructed of a piezoelectric element which generates an AC signal when vibrated. Normal engine operation will cause the KS to generate signals of known frequencies. When engine knock is present, KS frequency changes. This signals the Powertrain Control Module (PCM) to retard ignition timing. PCM sends a bias voltage of 5 volts to the KS on KS signal high circuit. PCM expects approximately 2.5 volts back on KS signal low circuit. KS generated AC signal rides on top of bias voltage provided by the PCM.
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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.