P0314
Single Cylinder Misfire (Cylinder not Specified)P0314 is a generic OBD-II powertrain diagnostic trouble code: Single Cylinder Misfire (Cylinder not Specified). It is logged by the engine control unit when the misfire monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0314 means
P0314 is an OBD-II powertrain code indicating the engine control module has detected a misfire in a single cylinder but is unable to identify which specific cylinder is misfiring. This contrasts with codes P0301–P0312, where the ECM pinpoints the exact cylinder. P0314 is set when the crankshaft deceleration signature is consistent with a single-cylinder event but the cam-crank correlation data needed to assign that event to a specific cylinder is absent, ambiguous, or contradictory — for example due to a degraded camshaft position sensor signal, crankshaft reluctor tooth damage, or severe sensor noise occurring at the moment of misfire detection.
A less common trigger scenario is a multi-cylinder misfire pattern that the ECM's misfire detection algorithm cannot resolve to any single cylinder — the deceleration events don't fit the expected spacing for any one cylinder's power stroke, so the module logs P0314 rather than assigning an incorrect cylinder number. P0314 may also appear when the crankshaft or camshaft position sensor is beginning to fail intermittently, corrupting the cylinder-identification reference just enough to prevent positive attribution without yet generating a sensor-specific fault code.
Repair strategy begins the same way as any cylinder-specific misfire: check the most probable ignition and fuel causes. However, diagnosing P0314 requires particular attention to the crankshaft and camshaft position sensors, their reluctor rings, and associated wiring, since the inability to identify the cylinder is itself a clue that the timing/position reference system has a problem. Running a cylinder contribution or power-balance test with a scan tool can often identify which cylinder is failing even when the ECM cannot do so automatically.
Common causes
Most-frequently reported root causes when P0314 is logged.
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1
Faulty or intermittently failing camshaft position sensor producing unreliable cylinder-identification reference signals.
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2
Damaged crankshaft reluctor ring with a missing, chipped, or worn tooth disrupting misfire-cylinder attribution.
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3
Crankshaft position sensor beginning to fail, generating noisy or dropout signals that corrupt cylinder tracking.
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4
Multiple cylinders misfiring simultaneously in a pattern the ECM algorithm cannot resolve to a single cylinder.
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5
Worn spark plug(s) or ignition coil(s) causing misfires that shift between cylinders before the ECM accumulates enough data to identify one.
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6
Low compression on one cylinder — from a worn valve, rings, or head gasket — causing a single-cylinder misfire the ECM cannot attribute due to sensor noise.
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7
Damaged or corroded wiring to either position sensor interrupting cam-crank synchronisation.
Symptoms drivers notice
How to diagnose P0314
A typical diagnostic flow when this code is present.
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1
Connect an OBD-II scan tool and confirm P0314; note any companion codes, especially crankshaft/camshaft position sensor codes (P0335–P0341) or additional misfire codes.
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2
Use the scan tool's cylinder contribution or power-balance test to artificially kill each cylinder in turn and measure the RPM drop — this identifies the weak cylinder even when the ECM cannot.
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3
Inspect the crankshaft reluctor ring (tone wheel) for chipped, missing, or damaged teeth using a bore scope or by feel with the crank sensor removed.
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4
Test the crankshaft and camshaft position sensors with an oscilloscope at idle to confirm clean, consistent waveforms without dropouts or noise spikes.
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5
Perform a spark plug and ignition coil inspection on all cylinders; replace any that show wear, cracking, or abnormal electrode gap.
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6
Run a compression and leak-down test across all cylinders to rule out mechanical causes and identify the misfiring cylinder by low compression.
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7
After repairs, clear codes and perform a road test monitoring per-cylinder misfire counters to verify the fault does not return as a numbered cylinder code.
Related powertrain codes
Frequently asked questions
Why can't the ECM tell which cylinder is misfiring?
The ECM uses cam and crank sensor signals together to determine which cylinder is on its power stroke at the moment of each crankshaft deceleration event. If either sensor signal is noisy, intermittent, or the reluctor ring is damaged, the ECM loses the reference needed to assign the deceleration to a specific cylinder — so it stores P0314 instead of a numbered code.
Is P0314 more serious than a numbered misfire code like P0301?
Not inherently more serious in terms of combustion damage, but it is potentially more complex to diagnose because it suggests a problem with the position sensing system in addition to (or instead of) a simple ignition or fuel component failure.
Can P0314 appear together with numbered misfire codes?
Yes. It is common for P0314 to appear alongside P0300 (random/multiple misfire) and occasionally with specific cylinder codes. When a sensor begins to fail intermittently, some misfires are attributed and some are not, resulting in a mix of codes.
Will replacing the crankshaft position sensor always fix P0314?
Not always. If the reluctor ring itself is damaged, a new sensor will still read incorrect signals from the damaged teeth. Both the sensor and the reluctor ring must be inspected. Additionally, if the misfire is caused by an ignition or fuel fault, fixing the sensor will not stop the underlying misfire.
Disabling P0314 in software
RaceTune can permanently disable P0314 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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