P2343: Cylinder 8 Above Knock/Combustion Vibration Sensor Threshold
What to do
Avoid heavy loads and ease off if you hear a rattle. If several cylinders on the same bank are reporting while the other bank is quiet, ask for that bank's knock sensor and its mounting to be checked first — one sensor covers a whole bank, and a poorly mounted one can produce codes across all the cylinders it listens to.
What this code means
Cylinder 8 is requiring more knock protection than normal. The mechanism is at P2336 and the shared-cause discriminator at P2341.
One thing is worth adding for engines with two knock sensors, which most eight-cylinder engines have: each sensor covers a bank, and the module assigns what it hears to a cylinder by timing. It knows which cylinder was firing when the noise arrived. That works well, but it means a sensor with degraded mounting or a damaged cable can misattribute noise — so where several cylinders on one bank report and the other bank is silent, the sensor serving that bank deserves checking before its cylinders do.
The mounting sensitivity that makes this matter is described at P0325: torque matters, and anything trapped between sensor and block stops it hearing the engine properly.
Likely causes
Start here
- Incorrect or low octane fuel · easy
- Faulty knock sensor · moderate
- Carbon deposits in the combustion chamber · moderate
Less common
- Clogged fuel injectors · moderate
- Damaged knock sensor wiring · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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