Failed or degraded knock sensor for cylinder two or its corresponding bank; Damaged, chafed, or loose knock sensor wiring or connector, allowing electrical noise to mimic knock; Carbon buildup or deposits in cylinder two raising compression and promoting detonation; Incorrect ignition timing or a faulty crankshaft/camshaft position sensor causing timing errors; Low fuel octane, contaminated fuel, or fuel delivery issues causing lean conditions in cylinder two; Mechanical noise from a failing lifter, piston slap, or loose internal component being interpreted as knock; Faulty ECM or knock sensor module calibration, though this is the least likely cause

DTC codes / P23xx · Ignition system and misfire / P2337

P2337Cylinder #2 Above Knock Threshold

Q: What does code P2337 mean?

Cylinder #2 Above Knock Threshold. P2337 is a generic powertrain code that the engine control module (ECM) sets when the knock sensor signal for cylinder number two exceeds the calibrated knock threshold, indicating abnormal combustion or excessive vibration. The computer is not simply hearing a noise; it is comparing the knock sensor waveform during the cylinder two firing window against a stored limit and flagging the event as a knock event that is too severe or too frequent.

P2337 is a generic powertrain code that the engine control module (ECM) sets when the knock sensor signal for cylinder number two exceeds the calibrated knock threshold, indicating abnormal combustion or excessive vibration. The computer is not simply hearing a noise; it is comparing the knock sensor waveform during the cylinder two firing window against a stored limit and flagging the event as a knock event that is too severe or too frequent.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illumination of the check engine light, often with no other symptoms besides the warning light
Audible pinging, rattling, or knocking from the engine under acceleration or load
Reduced engine power or sluggish acceleration as the ECM retards ignition timing to protect the engine
Rough idle or misfire-like shudder that may be intermittent
Poor fuel economy or increased fuel consumption over time
In severe cases, a flashing check engine light if knock escalates to misfire or catalyst-damaging conditions

Common causes, most likely first

Failed or degraded knock sensor for cylinder two or its corresponding bank
Damaged, chafed, or loose knock sensor wiring or connector, allowing electrical noise to mimic knock
Carbon buildup or deposits in cylinder two raising compression and promoting detonation
Incorrect ignition timing or a faulty crankshaft/camshaft position sensor causing timing errors
Low fuel octane, contaminated fuel, or fuel delivery issues causing lean conditions in cylinder two
Mechanical noise from a failing lifter, piston slap, or loose internal component being interpreted as knock
Faulty ECM or knock sensor module calibration, though this is the least likely cause

How to diagnose and fix it

Connect a scan tool and record freeze-frame data for P2337, then verify the knock sensor signal with a oscilloscope or live data to confirm real knock versus false signal
Inspect the knock sensor for cylinder two, checking mounting torque, condition, and that no thread sealant or debris is insulating it from the block
Check the knock sensor wiring harness for chafing, loose pins, or poor grounds, and perform a voltage drop test on the sensor circuit
Verify fuel quality and octane rating, then inspect for vacuum leaks or fuel delivery problems that could cause a lean condition in cylinder two
Perform a cylinder balance or compression test on cylinder two to rule out mechanical noise sources such as carbon buildup or internal damage
If the sensor and wiring are good, check ignition timing and the crankshaft/camshaft sensor signals for timing errors that could induce knock
Replace the knock sensor only after confirming the signal is faulty, then clear codes and road-test under load to verify the repair

Before you replace the knock sensor

A loose knock sensor or one installed with thread sealant can produce a false high signal that sets P2337 even though the sensor itself is healthy.
Carbon deposits in cylinder two are a common hidden cause because they raise the effective compression ratio and create hot spots that trigger detonation without any sensor fault.
Electrical noise from a failing alternator or ignition component can be picked up by the knock sensor circuit and misread as knock, so always check charging system ripple.
P2337 does not always mean the engine is actually knocking; a faulty sensor or wiring can report above-threshold vibration when combustion is normal.
Replacing the knock sensor without addressing a lean fuel condition or incorrect timing will usually result in the code returning within a few drive cycles.

Can I keep driving with P2337?

You can usually drive the vehicle to a repair shop, but avoid heavy acceleration, towing, or high-load conditions that provoke knock until the fault is diagnosed. If the check engine light flashes or you hear loud knocking, stop driving and have the vehicle towed to prevent engine damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.