Cylinder 12 Above Knock Threshold
P2347 indicates that the knock sensor for cylinder 12 is detecting excessive detonation (engine knock) beyond normal parameters. The PCM monitors knock sensor voltage to prevent engine damage from pre-ignition, and this code means the knock signal is abnormally high, suggesting either actual detonation occurring or a faulty sensor sending erratic signals.
What You Might Notice
- Engine knocking or pinging noise under load or acceleration
- Reduced engine performance and power
- Decreased fuel efficiency
- Rough idle or hesitation during acceleration
- Check Engine light illuminated
Most Common Causes
- 1
Faulty Knock Sensor
The knock sensor for cylinder 12 may be failing or sending incorrect voltage signals to the PCM. A worn or damaged sensor can register false knock events even when the engine is running normally.
- 2
Actual Engine Detonation
Fuel with insufficient octane rating, carbon buildup in combustion chambers, or incorrect ignition timing can cause real knock events. The sensor is detecting legitimate detonation that requires fuel or ignition correction.
- 3
Knock Sensor Wiring or Connection Issues
Corroded, loose, or damaged wiring on the knock sensor circuit can cause voltage fluctuations that trigger the code. A poor ground connection or damaged connector may send false signals to the PCM.
- 4
Engine Carbon Buildup or Internal Issues
Excessive carbon deposits in cylinder 12 or internal engine damage can create abnormal combustion patterns that the knock sensor interprets as severe detonation. This requires more extensive engine diagnostics.
How to Diagnose It
- 1
Check Faulty Knock Sensor — The knock sensor for cylinder 12 may be failing or sending incorrect voltage signals to the PCM. A worn or damaged sensor can register false knock events even when the engine is running normally.
- 2
Check Actual Engine Detonation — Fuel with insufficient octane rating, carbon buildup in combustion chambers, or incorrect ignition timing can cause real knock events. The sensor is detecting legitimate detonation that requires fuel or ignition correction.
- 3
Check Knock Sensor Wiring or Connection Issues — Corroded, loose, or damaged wiring on the knock sensor circuit can cause voltage fluctuations that trigger the code. A poor ground connection or damaged connector may send false signals to the PCM.
- 4
Check Engine Carbon Buildup or Internal Issues — Excessive carbon deposits in cylinder 12 or internal engine damage can create abnormal combustion patterns that the knock sensor interprets as severe detonation. This requires more extensive engine diagnostics.
How to Fix It
- 1
Inspect and Replace Knock Sensor
Remove the knock sensor from cylinder 12 and inspect it for damage, corrosion, or wear. Test the sensor resistance with a multimeter, and replace it if readings are outside manufacturer specifications or the sensor is visibly damaged.
- 2
Check and Repair Sensor Wiring
Inspect the knock sensor harness and connector for corrosion, loose pins, or damage. Repair any damaged wiring, clean corroded connectors, and ensure a solid ground connection to the engine block.
- 3
Verify Fuel Quality and Octane Rating
Drain the fuel tank and refill with high-octane fuel (91 octane or higher, depending on vehicle requirements). Low-octane fuel can cause genuine detonation that triggers knock sensors even on properly functioning engines.
- 4
Perform Engine Carbon Cleaning
If knock is confirmed through diagnostic testing, clean carbon buildup from the combustion chambers using fuel system cleaner additive or professional fuel injection service. Severe buildup may require valve and chamber cleaning.
Need a deeper diagnosis?
Search for related repair guides or browse by system.