P2345 – Cylinder 10 Above Knock Threshold

System: Powertrain | Standard: ISO/SAE Controlled | Fault type: General | Location: Cylinder 10

Definition source: SAE J2012/J2012DA (industry standard)

DTC P2345 indicates the control module has detected that combustion knock for cylinder 10 is above an allowed threshold under the conditions where the monitor runs. This is a fault related to knock intensity for a specific cylinder, not a generic “engine noise” statement, and it does not by itself prove a particular mechanical failure. The exact enable criteria, how quickly the code sets, and what data is stored (freeze-frame, misfire counters, knock feedback) can vary by vehicle, so confirm the monitor description and test specifications in the appropriate service information before making repairs.

What Does P2345 Mean?

P2345 means Cylinder 10 Above Knock Threshold. In practical diagnostic terms, the powertrain control module has determined that knock activity attributed to cylinder 10 exceeded the calibrated limit during monitored operation. SAE J2012 defines how DTCs are structured and identified, but the specific threshold logic, filtering, and operating conditions used to decide “above knock threshold” are vehicle-dependent. Treat this code as a detected condition requiring verification with scan data and testing rather than assuming a single root cause.

Quick Reference

• System: Powertrain
• Official meaning: Cylinder 10 Above Knock Threshold
• Standard: ISO/SAE controlled
• Fault type: General
• Severity: MIL illumination is possible; continued operation under knock can lead to reduced performance and, if severe or persistent, potential engine damage.

Symptoms

• MIL/Check Engine: Warning light may illuminate and P2345 may store as pending or confirmed.
• Reduced power: Engine may limit torque or feel less responsive if knock control is actively intervening.
• Audible ping: Metallic rattling or pinging under load may be noticeable, especially during acceleration.
• Roughness: Possible vibration, uneven running, or harshness that may be more apparent under load.
• Poor fuel economy: Increased fuel consumption may occur if timing is being retarded to manage knock.
• Hard acceleration issues: Hesitation, surging, or lack of pull may be present during higher-load events.
• Related codes: Additional faults may appear (varies by vehicle), such as misfire, fuel trim, or knock sensor-related codes.

Common Causes

• Damaged wiring: Harness chafing, pinched sections, or heat damage affecting the cylinder 10 knock sensor signal circuit.
• Connector problems: Loose connectors, poor terminal tension, corrosion, moisture intrusion, or bent/partially backed-out pins at the knock sensor or control module.
• Signal circuit short: Short-to-ground or short-to-voltage on the knock sensor signal line causing an abnormal reading or distorted waveform.
• Reference/ground faults: Sensor ground issues, shared ground contamination, or poor engine ground paths that introduce noise and false knock indications.
• Knock sensor fault: Internal sensor failure, incorrect installation/torque (varies by vehicle), or sensor damage leading to biased output.
• Mechanical noise: Valve train noise, exhaust contact, accessory/bracket rattles, or internal engine noise being interpreted as knock on cylinder 10.
• Combustion-related knock conditions: Abnormal combustion (for example, incorrect fuel quality, overheating, or improper ignition/fueling control) increasing knock intensity on cylinder 10.
• Calibration/adaptation issues: Control module learned values or adaptive strategies out of range after repairs or battery events (varies by vehicle).
• Control module issue: Rare internal control module fault or software anomaly affecting knock detection and cylinder attribution.

Diagnosis Steps

Tools that help include a scan tool with live data and freeze-frame access, a multimeter for continuity and voltage-drop checks, and basic back-probing supplies. If available, an oscilloscope can be useful for viewing the knock sensor signal pattern under load. Use service information for connector pinouts, wiring routing, and any required test conditions or relearn procedures.

1. Confirm the code and context: Scan for P2345 and record freeze-frame data, including engine speed, load, coolant temperature, and any spark retard/knock-related parameters available.
2. Check for related DTCs: Note misfire, fuel trim, cooling system, ignition, or sensor reference/ground DTCs. Diagnose supporting codes first if they can drive knock detection or noise sensitivity.
3. Review live data at idle: Observe knock-related PIDs (if supported) for cylinder-specific activity and overall knock control behavior. Look for implausible readings (stuck, erratic, or excessively noisy signals) before commanding any changes.
4. Perform a thorough visual inspection: Inspect the harness and connectors for the cylinder 10 knock sensor circuit (routing varies by vehicle). Look for rubbed-through insulation, contact with hot surfaces, oil saturation, broken clips, or signs of previous repairs.
5. Connector and terminal checks: With the ignition off, disconnect and inspect terminals for corrosion, spread pins, moisture, and poor retention. Verify connectors fully seat and lock; correct any pin-fit issues found.
6. Wiggle test with live logging: Log knock-related PIDs and/or the sensor signal parameter (if available) while gently flexing the harness and tapping near suspected rub points. If readings change abruptly or the code resets, focus on that section of wiring/connector.
7. Continuity and short checks: Using the wiring diagram, test the knock sensor signal circuit for continuity end-to-end and for shorts to ground or shorts to power. Repair any opens/high resistance or shorts before continuing.
8. Voltage-drop testing of grounds: With the engine running (and electrical loads applied as appropriate), perform voltage-drop tests across engine/chassis grounds and sensor ground paths related to the knock detection circuit. Excessive drop indicates a ground path problem that can introduce noise.
9. Evaluate sensor operation: If access permits and service information supports it, check the sensor and mounting area for damage or looseness. If using an oscilloscope, look for a stable baseline and reasonable response to engine conditions; compare to known-good behavior where possible.
10. Rule out mechanical noise sources: Inspect for exhaust contact, loose heat shields, brackets, or accessory noise that could be interpreted as knock. Correct obvious noise sources and re-test, as non-combustion vibrations can trigger above-threshold detection.
11. Check combustion contributors: Verify cooling system operation, intake leaks, and ignition/fueling basics (as applicable) to ensure the engine is not operating in a way that promotes knock. Use service information to guide any targeted checks.
12. Clear codes and verify: After repairs, clear DTCs and perform a drive cycle or test procedure that reproduces the original conditions in the freeze-frame. Re-scan to confirm P2345 does not return and review readiness/monitors as applicable.

Professional tip: If P2345 is intermittent, prioritize repeatable evidence: capture freeze-frame, save a short live-data log, and document exactly which harness movement or operating condition changes the knock signal. That approach helps distinguish true knock/noise conditions from wiring/ground faults and prevents unnecessary parts replacement.

Possible Fixes & Repair Costs

Repair costs for P2345 can vary widely because the root cause may be wiring-related, sensor-related, or due to a true knock condition on cylinder 10. Parts access, required testing time, and labor rates also affect total cost, so diagnose first before replacing components.

• Repair wiring/connector issues: Repair damaged harness sections, restore proper pin fit, clean corrosion, and ensure connectors are fully seated and secured for the knock sensing circuit and related engine wiring.
• Restore power/ground integrity: Correct poor grounds, loose fasteners, or high-resistance connections found during voltage-drop testing that can distort sensor signals or control module processing.
• Replace the knock sensor (if verified): Replace only if testing confirms the sensor is out of specification, physically damaged, or produces an erratic/biased signal compared with expected behavior.
• Correct mechanical contributors to knock: Address verified causes such as ignition timing control faults, improper spark plug condition/type/gap (varies by vehicle), combustion deposits, or cooling system issues that can raise knock tendency.
• Resolve fueling issues: Repair confirmed problems that can promote knock, such as injector performance issues on cylinder 10, fuel pressure/regulator faults, or intake air leaks affecting mixture control.
• PCM/ECM update or replacement (rare): Consider only after all circuit and mechanical checks pass and the fault is repeatable; follow service information for reprogramming, setup, and relearn procedures.

Can I Still Drive With P2345?

You may be able to drive short distances if the vehicle feels normal, but P2345 indicates cylinder 10 knock above a calibrated threshold and continued operation under knock can lead to protective power reduction and potential engine damage. Avoid heavy throttle, towing, or high-load operation until diagnosed. If you notice severe misfire, reduced power, overheating, abnormal noises, or any safety-related warnings, do not drive and arrange service.

What Happens If You Ignore P2345?

Ignoring P2345 can allow persistent knock or a faulty knock detection signal to continue, which may cause the control system to retard timing, reduce performance, and increase fuel consumption. If the underlying issue is true knock, prolonged operation can accelerate wear or lead to internal engine damage. If the issue is electrical or signal-related, you may also experience intermittent drivability concerns and repeated MIL illumination.

Last updated: February 16, 2026

Vehicles Commonly Affected by P2345

• Vehicles equipped with a cylinder 10: Typically engines with ten or more cylinders, where cylinder numbering and bank layout vary by vehicle.
• Models using knock-based spark control: Platforms that actively adjust ignition timing based on knock sensing feedback under load.
• High-load duty applications: Vehicles frequently operated under sustained load, towing, or heavy acceleration where knock control is more active.
• Vehicles with aging engine harnesses: Heat and vibration can degrade insulation, connector seals, and terminal tension over time.
• Vehicles exposed to moisture/corrosion: Environments that promote connector corrosion or ground path degradation can affect sensor signal quality.
• Engines sensitive to cooling/fueling condition: Systems where small deviations in mixture control, cooling performance, or ignition components can increase knock tendency.
• Vehicles with recent engine work: Harness routing, connector seating, or component torque/installation issues (varies by vehicle) can impact knock sensing reliability.

For best results, address P2345 with a test-driven approach that confirms whether the issue is true knock on cylinder 10 or a problem with the knock detection signal and its supporting circuits.