OBD-II trouble code
P0314: Single Cylinder Misfire (Cylinder Not Specified)
One cylinder is misfiring and the module cannot say which one. The inability to name it is not a limitation to work around — it is usually the most informative part of the code.
Quick facts
- System
- Powertrain
- Category
- Ignition / Misfire
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $120 – $2,500
- DIY difficulty
- Intermediate DIY
What does P0314 mean?
Counting misfires and identifying misfires are two different capabilities, and P0314 is what happens when an engine controller has the first and not the second. Counting only requires the crankshaft signal: the module sees an acceleration shortfall and knows a cylinder failed to contribute. Identifying requires knowing where in the four-stroke cycle the engine was at that instant, which takes a valid camshaft signal correlated against the crankshaft, plus a learned crankshaft variation table so that reluctor tolerance is not mistaken for combustion loss. Lose any part of that second chain and the module retains the count while losing the name.
This is why P0314 so often turns up in company rather than alone. A camshaft position correlation code, a crank sensor code, an unfinished variation relearn, or a timing chain that has stretched enough to shift the cam-to-crank relationship will each produce exactly this outcome. When P0314 appears next to any of them, the right sequence is to restore identification first and then re-read the codes, because the moment the module can name the cylinder it will, and the diagnosis becomes an ordinary single-cylinder misfire with a number attached.
There is a second population where nothing is broken at all. Some engine calibrations simply do not support per-cylinder attribution — the crank wheel does not carry enough resolution, or the application has no cam-based identification to correlate against — and on those vehicles P0314 is the only misfire code the module can set for a single cylinder. It is normal behaviour for that platform, not a fault in the monitoring system, and the diagnosis proceeds by manual elimination instead: disable one injector at a time and watch which one makes no difference, or compare relative compression across all cylinders from the scan tool's cranking data.
The practical warning is that this code carries the same downstream risk as any named misfire. Raw fuel entering a hot catalytic converter does not care whether the module identified its cylinder of origin, and the fact that the code cannot point at a cylinder makes it tempting to postpone. Treat P0314 with the urgency you would give P0301.
Common causes
- Camshaft position sensor fault or cam-to-crank correlation drift preventing cylinder identification
- Crankshaft position sensor signal degradation or a damaged reluctor wheel
- Crankshaft variation relearn never performed after sensor, balancer, flexplate or module work
- Stretched timing chain or worn tensioner shifting the cam relationship out of tolerance
- Genuine single-cylinder misfire on a platform whose calibration cannot attribute cylinders
- Failing ignition coil, spark plug or fuel injector on an unidentified cylinder
- Low compression on one cylinder
- Intermittent wiring or connector fault in the camshaft or crankshaft sensor circuit
Symptoms
- Check engine light on, flashing while the misfire is active
- Rough idle and a perceptible vibration at low engine speed
- Hesitation or loss of power under acceleration
- Longer cranking time before the engine starts, where cam identification is also affected
- Misfire readiness monitor failing to complete
- Increased fuel consumption
- No specific cylinder code stored despite obvious misfire behaviour
Diagnostic steps
- 1.Read every stored code, including pending and history codes, and note the order they set in. A camshaft or crankshaft code alongside P0314 is the lead, not a side issue.
- 2.Check whether this vehicle is capable of per-cylinder misfire attribution at all. Manufacturer service information will say so, and knowing the answer decides whether you are repairing something or working around a design limit.
- 3.Verify that the crankshaft variation relearn has been completed, particularly if the crank sensor, harmonic balancer, flywheel or engine controller has been replaced.
- 4.Inspect the camshaft and crankshaft sensor connectors and their shielding. These are low-level signals and a marginal connection degrades identification before it degrades running.
- 5.Compare camshaft and crankshaft signal alignment on a scope or with the scan tool's cam-crank correlation data. Timing chain wear shows here before it shows anywhere else.
- 6.If identification is genuinely unavailable on the platform, isolate manually: run relative compression across all cylinders, then perform an injector-disable test one cylinder at a time and note which disable produces no change in engine speed.
- 7.Once the cylinder is identified by either route, treat it as a standard single-cylinder misfire and triage spark, fuel and compression in that order.
Repair cost
$120 – $2,500
The distribution here is bimodal. If the code is really about lost cylinder identification, the fix is often modest: a camshaft or crankshaft position sensor is $150 to $450 fitted, and a crankshaft variation relearn is frequently under $150 as a scan tool procedure. If the code is a genuine misfire on a platform that cannot name cylinders, expect $100 to $200 of extra diagnostic time on top of the repair because the cylinder has to be found manually. Timing chain work, where chain stretch is the reason identification failed, is the expensive tail at $1,200 to $2,500 and up.
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DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.