P2337 – Cylinder 2 Above Knock Threshold

System: Powertrain | Standard: ISO/SAE Controlled | Fault type: General | Location: Cylinder 2

Definition source: SAE J2012/J2012DA (industry standard)

DTC Structure (SAE J2012)

• P = Powertrain
• 2 = ISO/SAE Controlled
• 337 = Specific fault index for this code
• Fault type = General

3-byte note: Some platforms may report a 3-byte DTC with an added Failure Type Byte (FTB) suffix like -1A. Treat the base code and the FTB as separate: the base code identifies the subsystem; the FTB refines the failure subtype.

DTC P2337 is a powertrain diagnostic code that indicates the control module has detected knock activity on cylinder 2 that is above an expected threshold. This is not the same as confirming mechanical damage or poor fuel quality by itself; it only means the monitored knock level for that cylinder exceeded the calibrated limit under certain operating conditions. How the threshold is determined, what sensors are used, and what enabling conditions must be met can vary by vehicle. Always verify the exact diagnostic routine, test criteria, and required repairs using the applicable service information.

What Does P2337 Mean?

P2337 – Cylinder 2 Above Knock Threshold means the engine control system has identified that the knock signal attributed to cylinder 2 exceeded the programmed knock threshold. Per SAE J2012, the DTC format standardizes how codes are named and organized, while the underlying detection logic is implemented by the vehicle’s control module strategy. In practice, the module evaluates knock-related input(s) and operating conditions (such as load and speed) and sets P2337 when cylinder 2 is determined to be above the allowable knock level for the conditions observed.

Quick Reference

• System: Powertrain
• Official meaning: Cylinder 2 Above Knock Threshold
• Standard: ISO/SAE controlled
• Fault type: Plausibility
• Severity: MIL may illuminate; engine power reduction and drivability changes are possible if the control module actively limits load or increases spark retard to protect the engine.

Symptoms

• MIL/Check engine: Warning lamp may turn on, sometimes after specific load or temperature conditions are met.
• Reduced power: Noticeable loss of acceleration if the system retards ignition timing or limits torque in response to detected knock.
• Roughness: Engine may feel rough or uneven under acceleration, especially when cylinder 2 is contributing differently than the others.
• Pinging/rattle: Audible knock may be present under load, though some vehicles mask it with control strategies.
• Poor fuel economy: Increased fuel consumption can occur due to spark retard and altered combustion efficiency.
• Intermittent hesitation: Hesitation or stumble may appear during tip-in or when climbing grades where knock control is most active.

Common Causes

• Knock sensor circuit wiring fault: Damaged insulation, chafing, pinched harness, or broken conductors affecting the knock sensor signal path used to evaluate cylinder-specific knock.
• Connector issues: Loose connectors, poor pin fit, corrosion, or terminal push-out at the knock sensor, intermediate junctions, or control module connections.
• Reference/ground integrity problem: Shared sensor grounds or reference circuits with excessive resistance, poor ground attachment, or internal splice issues that distort the knock signal.
• Knock sensor mounting/installation concern: Incorrect torque, wrong mounting surface condition, or mechanical coupling issues that change sensor sensitivity (varies by vehicle).
• Actual abnormal combustion in cylinder 2: Detonation/knock events due to operating conditions or engine mechanical/fueling factors; must be confirmed with scan data and inspection, not assumed from the DTC alone.
• Ignition system fault affecting cylinder 2: Spark plug, coil/boot, or related wiring causing misfire-like combustion irregularities that can be interpreted as knock.
• Fuel delivery or injector issue on cylinder 2: Restricted/imbalanced fueling or injector electrical/mechanical concerns that alter combustion behavior.
• Engine mechanical or base condition issue: Compression imbalance, vacuum leaks affecting one runner (design-dependent), or timing-related problems that can increase knock tendency.
• Control module/software or signal processing issue: Internal control module fault or calibration issue (less common); confirm power/grounds and signal integrity first.

Diagnosis Steps

Tools: A scan tool with live data and freeze-frame access, a digital multimeter, and basic hand tools are typically required. An oscilloscope is helpful for verifying knock sensor signal quality and noise. Use service information for connector pinouts, wiring colors, and test procedures. If available, use data logging to capture knock-related parameters during a controlled road test.

1. Confirm the code and capture data: Verify P2337 is present. Record freeze-frame data, pending codes, and any related powertrain codes (misfire, fuel trim, ignition, or sensor codes) to guide the diagnostic path.
2. Check for technical updates and code criteria: Consult service information for the exact enable conditions and detection logic for “Cylinder 2 Above Knock Threshold,” since cylinder attribution and thresholds vary by vehicle and calibration.
3. Perform a visual inspection first: Inspect the knock sensor harness routing and connectors for rub-through, heat damage, oil saturation, corrosion, and loose locking tabs. Pay close attention to areas near the engine block, brackets, and exhaust shielding.
4. Wiggle test while monitoring live data: With the engine running (or key on as applicable), gently move the harness and connectors while watching knock-related PIDs and misfire counters. If the reading spikes or the fault toggles, isolate the affected section and connector.
5. Verify power and ground integrity (where applicable): Using the wiring diagram, confirm sensor grounds and any reference feeds are present and stable. Perform voltage-drop testing on the relevant grounds under load to identify high resistance that could distort the knock signal.
6. Check signal circuit continuity and for shorts: With the circuit safely disabled as directed by service information, test for opens, high resistance, and shorts-to-ground/shorts-to-power on the knock sensor signal wiring between the sensor and the control module.
7. Assess knock sensor installation and mechanical coupling: Verify the sensor is correctly mounted and secured per service information. If the design uses a specific mounting boss, washer, or torque procedure, confirm it is correct; improper coupling can change sensitivity and cause false knock interpretation.
8. Evaluate cylinder 2 combustion inputs: Review live data for misfire counters, ignition timing, fuel trims, and any available cylinder-specific data. If cylinder 2 shows abnormal behavior, inspect ignition components and fueling for that cylinder and correct verified faults before replacing sensors.
9. Use scope testing if available: Compare knock sensor waveform behavior during steady RPM and light load versus a controlled snap throttle (as permitted). Look for noise, dropouts, or irregular signal patterns that correlate with harness movement or specific operating conditions.
10. Clear codes and perform a verification drive: After repairs, clear DTCs and run the vehicle through the enable conditions noted in service information. Recheck for returning DTCs and confirm live data remains stable without abnormal knock indications for cylinder 2.

Professional tip: Treat P2337 as a “prove it” code: confirm signal integrity and ground quality first, then use logged data to separate false knock (wiring/installation/noise) from real knock events. If you replace parts without validating the circuit and mounting, the code can return because the underlying signal distortion or ground resistance remains.

Possible Fixes

• Repair wiring/connector issues: Restore damaged insulation, corroded terminals, loose pin fit, or poor grounds related to the knock sensing circuit and engine control connections that affect cylinder-specific knock evaluation.
• Address ignition-related contributors: If testing confirms misfire or abnormal ignition behavior on cylinder 2, replace worn ignition components and correct coil/driver concerns per service information.
• Correct fuel delivery problems: If verified by scan data and fuel system tests, repair the cause of lean operation on cylinder 2 (such as injector faults, restricted fuel supply, or air leaks affecting that cylinder).
• Resolve mechanical contributors: If mechanical testing indicates an abnormality (compression/leak-down, valve timing, carbon buildup, cooling system issues), perform the appropriate mechanical repair before re-evaluating knock behavior.
• Knock sensor/service actions: If diagnostics confirm a sensor fault or mounting issue (varies by vehicle), replace the sensor and/or correct installation/torque and harness routing as specified.
• Control module updates or replacement: If all inputs are verified and the condition persists, check for applicable calibration updates; replace the control module only after confirming power/ground integrity and completing manufacturer-directed tests.

Can I Still Drive With P2337?

Driving may be possible for a short distance if the vehicle feels normal and no warning indicators suggest reduced power or severe misfire, but you should minimize load and avoid hard acceleration because the condition involves cylinder 2 exceeding the knock threshold. If you have flashing MIL behavior, strong hesitation, loud knocking/pinging, reduced-power operation, stalling, or any brake/steering warnings, do not continue driving; stop safely and arrange diagnosis. Continued driving under heavy load can increase the chance of drivability issues and potential engine damage depending on the root cause.

What Happens If You Ignore P2337?

Ignoring P2337 can lead to ongoing knock control intervention, reduced performance, poorer fuel economy, and higher exhaust emissions. If the underlying cause is lean operation, ignition problems, cooling concerns, or mechanical issues, sustained operation can accelerate wear and may damage engine components over time. Intermittent wiring or connector faults can also worsen, turning an occasional fault into frequent MIL events and more pronounced drivability symptoms.

Last updated: February 14, 2026