P2344
Cylinder 9 Above Knock/Combustion Vibration Sensor Threshold
Ignition / knock control
Generic OBD-II
Medium
What it means
P2344 means the knock sensor is detecting vibration on cylinder 9 above the allowed threshold — in other words, likely detonation ("knock"). The ECM responds by retarding timing, which cuts power. Causes range from low-octane fuel, carbon buildup, or a lean/hot combustion condition to a faulty knock sensor. Ongoing real knock can damage the engine, so it's worth diagnosing.
Medium
Can I keep driving? Drivable, but the ECM is pulling timing to protect the engine, so you'll feel reduced power — avoid heavy loads and use the correct-octane fuel until it's fixed.
Common symptoms
What you'll notice
- Check-engine light on
- Reduced power as the ECM retards ignition timing
- Pinging or knocking noise under load or acceleration
- Possible drop in fuel economy
Common causes
Most likely first
- Genuine detonation on cylinder 9 from carbon buildup or excessive combustion heatLikely
- Low-octane or poor-quality fuelCommon
- Lean mixture or over-advanced timing on that cylinderCommon
- Faulty knock sensor or its wiring/connectorLess often
- Cooling or EGR problems raising combustion temperatureLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data to see the conditions when knock was detected.
- Try a tank of the manufacturer-recommended octane fuel and a quality fuel-system cleaner.
- Check for lean-running or misfire codes that could cause detonation on that cylinder.
- Inspect the knock sensor, wiring, and connector; compare live knock data with a scan tool.
- If knock persists with good fuel and a healthy sensor, investigate carbon buildup, cooling, and timing. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2344?+
Short-term yes, because the ECM retards timing to prevent damage — but that reduces power. Sustained real detonation can harm pistons and rings, so don't ignore it.
Can I just clear P2344?+
You can, but it returns if the cause (fuel quality, carbon, timing, or a bad sensor) isn't addressed.
Related codes
Often seen with P2344
Read & clear P2344 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