P2345 — Cylinder 10 Above Knock Threshold
P2345 — Cylinder 10 Above Knock Threshold. A fault in the knock (detonation) detection. Short, gentle driving to a shop is usually possible. Typical causes: low-octane or contaminated fuel, failed knock sensor, loose sensor mounting or incorrect torque.
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 P2345 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 P2345 does not return.
Approximate repair cost
Repair cost depends on which component actually failed. Typical scenarios for P2345 (parts and labor, USD, independent shop rates): Decarbonization service: $150–$400; Replace the knock sensor: $150–$450; Repair sensor wiring: $80–$250. Overall, fixing P2345 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
How do I diagnose P2345 myself?
Start with a scan: confirm P2345, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the knock (detonation) detection, and verify the suspect component against live data before buying parts.
Will P2345 clear itself?
Sometimes P2345 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 is the most common cause of P2345?
The most common causes are: low-octane or contaminated fuel, failed knock sensor, loose sensor mounting or incorrect torque.
How much does it cost to fix P2345?
Decarbonization service — $150–$400; Replace the knock sensor — $150–$450; Repair sensor wiring — $80–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.
What does OBD2 code P2345 mean?
P2345 — Cylinder 10 Above Knock Threshold. A fault in the knock (detonation) detection. Short, gentle driving to a shop is usually possible. Typical causes: low-octane or contaminated fuel, failed knock sensor, loose sensor mounting or incorrect torque.
What does P2345 mean?
The engine control module sets P2345 when it detects a fault in the knock (detonation) detection. In practical terms: cylinder 10 above knock threshold. The code belongs to the powertrain (engine/transmission) group of OBD2 codes.
P2345 refers specifically to cylinder 10. 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.
This code does not appear from a single bad reading: the module must see the fault condition repeat under defined operating conditions before it turns on the warning light. The freeze frame captured with P2345 — engine load, rpm, temperature, speed — tells you exactly when the problem occurs, so reproduce those conditions when testing.
Common symptoms of P2345
- Check Engine Light on
- worse fuel economy
- often no audible symptoms
- reduced power (ECM retards timing)
- metallic pinging under acceleration
What causes P2345?
- damaged knock sensor wiring or connector
- engine carbon buildup causing real detonation
- low-octane or contaminated fuel
- loose sensor mounting or incorrect torque
- failed knock sensor
How to diagnose P2345
- Connect an OBD2 scanner, confirm P2345 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 P2345 does not return.
How to fix P2345
Start with the cheapest and most common causes before replacing expensive parts:
- Decarbonization service — $150–$400
- Replace the knock sensor — $150–$450
- Repair sensor wiring — $80–$250
How much does it cost to fix P2345?
Repair cost depends on which component actually failed. Typical scenarios for P2345 (parts and labor, USD, independent shop rates):
- Decarbonization service: $150–$400
- Replace the knock sensor: $150–$450
- Repair sensor wiring: $80–$250
Overall, fixing P2345 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 P2345?
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.