What Does P0314 Mean?
A misfire has been detected in one of the engine's cylinders, but the PCM cannot identify which specific cylinder is misfiring. This typically indicates the misfire detection system has identified combustion irregularities without enough data to isolate the offending cylinder. The driver may notice rough idle, hesitation under acceleration, or a flashing check engine light during misfire events.
Common Causes
30%
Worn or fouled spark plugs causing inconsistent ignition across multiple cylinders
25%
Failing ignition coil(s) with intermittent output breakdown
20%
Fuel delivery issue such as low fuel pressure or clogged injectors
15%
Vacuum leak causing lean condition affecting random cylinders
10%
Compression loss due to worn valve seats or piston rings
Diagnostic Steps
1
Review Mode $06 misfire counter data to identify which cylinders have the highest misfire counts — this can help narrow down the unspecified cylinder.
2
Check live PID data for fuel trims (STFT and LTFT) on both banks; a lean condition over +10% suggests a vacuum leak or fuel delivery issue.
3
Perform a relative compression test using cranking RPM variation data available through the scan tool to identify weak cylinders.
4
Inspect spark plugs for fouling, wear, or damage; check gap against manufacturer specification (typically 0.028–0.032 inches for most applications).
5
Measure fuel pressure at the rail with a gauge; compare to specification (typically 55–62 PSI for port injection systems at idle with vacuum line connected).
Estimated Repair Cost
$100 - $800
Parts + labor, varies by vehicle and location
A misfire has been detected in one of the engine's cylinders, but the PCM cannot identify which specific cylinder is misfiring. This typically indicates the misfire detection system has identified combustion irregularities without enough data to isolate the offending cylinder. The driver may notice ...
The most common cause of P0314 (Single Cylinder Misfire (Cylinder not Specified)) is: Worn or fouled spark plugs causing inconsistent ignition across multiple cylinders
Typical repair costs for P0314 range from $100 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Driving with an active misfire can damage the catalytic converter from unburned fuel and may cause loss of power. If the check engine light is flashing, pull over and have the vehicle towed to prevent converter damage. Continued driving with a steady light is acceptable for short distances but should be diagnosed promptly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0314 to identify the root cause.
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Quick Info
Category
Powertrain
System
Ignition / Fuel System
Difficulty
Type
Generic (SAE)
Recommended Tools
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