P2347 — Cylinder 12 Above Knock Threshold
powertrain (engine/transmission)
Is it safe to drive?
Drive with caution Drive gently and avoid hard acceleration. With knock detection off, the engine is not protected from detonation — sustained pinging under load can damage pistons and bearings over time.
How to diagnose with an OBD scanner
- Read the code and freeze frame Connect an OBD2 scanner, confirm P2347 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
- Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
- Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the knock (detonation) detection for damage, corrosion, chafing or poor contact.
- Subsystem check Inspect the knock sensor connector and wiring — heat and vibration damage them often.
- Subsystem check Check sensor torque and mounting surface; an improperly seated sensor reads incorrectly.
- Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2347 does not return.
Approximate repair cost
Repair cost depends on which component actually failed. Typical scenarios for P2347 (parts and labor, USD, independent shop rates): Repair sensor wiring: $80–$250; Replace the knock sensor: $150–$450; Decarbonization service: $150–$400. Overall, fixing P2347 usually costs between $80 and $450. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.
Common questions
What is the most common cause of P2347?
The most common causes are: engine carbon buildup causing real detonation, damaged knock sensor wiring or connector, failed knock sensor.
Will P2347 clear itself?
Sometimes P2347 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.
What does OBD2 code P2347 mean?
Cylinder 12 Above Knock Threshold (P2347): a powertrain (engine/transmission) fault affecting the knock (detonation) detection. Short, gentle driving to a shop is usually possible. Most often caused by engine carbon buildup causing real detonation, damaged knock sensor wiring or connector, failed knock sensor.
What are the symptoms of P2347?
Drivers most often notice: reduced power (ECM retards timing), worse fuel economy, Check Engine Light on, metallic pinging under acceleration.
How much does it cost to fix P2347?
Repair sensor wiring — $80–$250; Replace the knock sensor — $150–$450; Decarbonization service — $150–$400. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.
What does P2347 mean?
Seeing P2347 on your scanner? The control unit has caught the knock (detonation) detection operating outside its calibrated window. The formal description is “Cylinder 12 Above Knock Threshold”, and the code is grouped under powertrain (engine/transmission) faults.
P2347 refers specifically to cylinder 12. On inline engines cylinders are counted from the front (belt end); on V-engines the numbering depends on the manufacturer, so check the firing-order diagram for your exact model. Location matters for the repair bill: some cylinders require intake manifold removal, which adds labor time.
The module monitors this system continuously while driving. When readings fall outside the expected range for a defined number of drive cycles, it stores P2347 and switches on the warning light. Freeze frame data saved with the code shows the exact conditions — rpm, load, temperature, speed — at the moment the fault was detected, which is the best starting point for diagnosis.
What causes P2347?
- loose sensor mounting or incorrect torque
- failed knock sensor
- engine carbon buildup causing real detonation
- damaged knock sensor wiring or connector
Common symptoms of P2347
- reduced power (ECM retards timing)
- worse fuel economy
- Check Engine Light on
- metallic pinging under acceleration
- often no audible symptoms
How to diagnose P2347
- Connect an OBD2 scanner, confirm P2347 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
- Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
- Visually inspect the wiring harness and connectors related to the knock (detonation) detection for damage, corrosion, chafing or poor contact.
- Inspect the knock sensor connector and wiring — heat and vibration damage them often.
- Check sensor torque and mounting surface; an improperly seated sensor reads incorrectly.
- Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2347 does not return.
How to fix P2347
Start with the cheapest and most common causes before replacing expensive parts:
- Repair sensor wiring — $80–$250
- Replace the knock sensor — $150–$450
- Decarbonization service — $150–$400
How much does it cost to fix P2347?
Repair cost depends on which component actually failed. Typical scenarios for P2347 (parts and labor, USD, independent shop rates):
- Repair sensor wiring: $80–$250
- Replace the knock sensor: $150–$450
- Decarbonization service: $150–$400
Overall, fixing P2347 usually costs between $80 and $450. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.
Can you drive with P2347?
Drive gently and avoid hard acceleration. With knock detection off, the engine is not protected from detonation — sustained pinging under load can damage pistons and bearings over time.