P2347 indicates that the engine control module has detected vibration levels from cylinder 12 that exceed the calibrated knock sensor threshold. This can mean actual combustion knock (detonation) is occurring in cylinder 12, or that the knock sensor or its circuit is producing a false signal. The code is only applicable to engines with a cylinder 12, typically V12 configurations.
Low-octane fuel, carbon deposits in the combustion chamber, a lean air-fuel mixture, or incorrect ignition timing can all produce true knock in cylinder 12 that the sensor correctly detects. This is one of the most common underlying causes.
The piezoelectric element inside the sensor can degrade, lose sensitivity, or fail internally, producing erratic voltage signals that the PCM interprets as knock.
Corroded, loose, or chafed wires between the sensor and PCM, or a poor connector fit, can create abnormal resistance and trigger false signals.
Loose accessories, worn valvetrain components, or a noisy accessory drive can produce vibrations that the sensor picks up and misinterprets as combustion knock.
If the sensor is over- or under-tightened, or its mounting surface is dirty, oily, or damaged, it will not accurately read block vibrations and may generate false codes.
Rare, but a failing PCM or corrupted calibration can misinterpret normal sensor signals as knock. This is typically diagnosed only after all other causes are ruled out.
No. Replacing the engine control module is one of the most expensive and least likely fixes for this code. The PCM is almost never the cause. The knock sensor, its wiring, sensor mounting, or actual combustion knock conditions are responsible in the vast majority of cases. Replacing the computer without first testing the sensor, wiring, fuel, and timing does not follow a sound diagnostic process.
If the code represents real engine knock, continued driving under load can damage pistons, bearings, or other components. If it is a false sensor signal, the risk is lower but performance and economy may still suffer. Address the code promptly and avoid heavy load operation until the cause is identified.
Yes. Low-octane or contaminated fuel is a common trigger for knock sensor codes. Switching to the manufacturer-specified minimum octane, or draining contaminated fuel, sometimes resolves the code without any sensor replacement.
On engines that use individual knock sensors or per-cylinder knock detection, the PCM reports which cylinder's sensor exceeded the threshold. The '12' simply indicates the issue was detected at that specific cylinder's sensor or in that cylinder's combustion event.