P2343
Cylinder 8 Above Knock/Combustion Vibration Sensor Threshold
Ignition / knock control
Generic OBD-II
Medium
What it means
P2343 means the knock sensor detected combustion vibration on cylinder 8 above the allowed threshold — the engine is knocking (pinging) there, or the sensor is reading a false high. The ECM retards timing to protect the engine, which trims power, so the cause should be tracked down before real detonation damages the piston.
Medium
Can I keep driving? Drivable, but the ECM is pulling timing on cylinder 8 to suppress knock — go easy on the throttle and avoid heavy loads until it is fixed.
Common symptoms
What you'll notice
- Check-engine light on
- Loss of power or dull acceleration
- Audible knock or ping under load in some cases
- Slightly reduced fuel economy
Common causes
Most likely first
- Actual detonation from low-octane fuel or carbon buildupLikely
- Lean fueling or an overheating condition on that cylinderCommon
- Faulty knock sensor or noisy signalCommon
- Corroded connector or wiring at the knock sensorLess often
- Cooling or mechanical issue raising combustion temperatureLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and note load and timing when the code set.
- Try a tank of the correct-octane fuel and re-test if knock is fuel-related.
- Inspect the knock sensor connector and wiring for corrosion or damage.
- Check for lean conditions, cooling problems, or heavy carbon deposits.
- Replace the knock sensor if its signal is faulty, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2343?+
Light driving is fine, but sustained real knock can damage pistons, so avoid hard acceleration until the cause is found.
Can I just clear P2343?+
It returns whenever the ECM again sees knock above threshold on cylinder 8 unless the cause is corrected.
Related codes
Often seen with P2343
Read & clear P2343 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX