P2E5F

Code

Generic P — Powertrain

Cylinder 7 Alternative Fuel Misfire Detected

Brand: Generic

Type: P — Powertrain

Views: UK: 15 EN: 31 RU: 22

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Page language: EN

Causes

Faulty ignition component on cylinder 7 (coil, plug, plug wire or coil-on-plug)
Faulty or clogged alternative-fuel injector/valve for cylinder 7
Low or inconsistent alternative fuel supply/pressure to cylinder 7 (regulator, rail, vaporizer)
Mechanical problems: low compression, burnt valve, piston damage, head gasket leak
Air inlet leak or excessive leak-down (vacuum leak, intake manifold gasket)
Engine timing or cam/crank correlation error

Symptoms

Check Engine/MIL illuminated (steady or flashing depending on severity)
Rough idle or vibration, especially at low RPM
Reduced power, hesitation, or surge under load
Increased fuel consumption and visible driveability issues
Poor cold/hot starting or extended crank time
Possible unusual noises from affected cylinder at high load

What to check

Read freeze-frame data and all stored codes (pending and permanent)
Inspect ignition components (spark plug, coil, leads) on cylinder 7 for wear or damage
Visually inspect wiring and connectors for cylinder 7 ignition and injector circuits
Swap coil and/or spark plug with another cylinder to see if code follows
Swap alternative-fuel injector/valve with another cylinder (if serviceable) to check if fault follows
Measure fuel pressure and regulator function for the alternative fuel system

Signal parameters

Crankshaft speed variation / misfire counter for cylinder 7 (from scan tool)
Relative compression or cylinder contribution percentage
Injector pulse width (ms) for cylinder 7 and neighboring cylinders
Ignition primary/secondary voltage and coil dwell/current
Alternative fuel rail/line pressure (kPa or psi) and regulator reference
Short-term and long-term fuel trims (STFT/LTFT) and oxygen sensor voltage or wideband AFR

Diagnostic algorithm

Connect a capable scan tool. Record freeze-frame data, misfire counts, fuel trim, and live data while reproducing the symptom.
Check for additional codes that narrow down ignition, fuel, or sensor faults (e.g., injector, crank/cam sensor, fuel system codes).
Visually inspect and test ignition components for cylinder 7: remove and inspect the spark plug, test coil resistance or swap coil with a known good cylinder to see if fault follows.
Inspect wiring and connectors for corrosion, damage, or poor grounding on the cylinder 7 ignition and injector circuits. Wiggle-test while monitoring live data for interruptions.
Test the alternative-fuel injector/valve at cylinder 7: listen for operation, measure resistance, swap with another cylinder if practical, and observe changes in misfire counts.
Measure alternative fuel system pressure and regulator operation under idle and load; check for leaks or pressure drop that could affect one cylinder.
Perform a compression test and/or leak-down on cylinder 7; compare to adjacent cylinders to identify mechanical faults.
Verify cam/crank correlation with a scope or advanced scan tool; correct timing or sensor alignment issues as needed.
If electrical and mechanical checks pass, inspect for contaminated or incorrect alternative fuel and verify any vaporizer/pressure regulator components (CNG/LPG-specific) are functioning.
After repairs, clear codes, perform a road test to confirm misfire no longer occurs, and re-scan to ensure no recurrence or catalyst-related codes.

Likely causes

Ignition coil or spark plug failure on cylinder 7 (most common)
Injector/valve for the alternative fuel at cylinder 7 sticking or leaking
Local compression loss in cylinder 7
Wiring/connector corrosion or intermittent open/short to coil or injector
Fuel pressure regulator or delivery problem specific to the alternative fuel system

Fault status

⚠️ Status

MIL (Check Engine) illuminated. ECU reports repeated misfire events detected on cylinder 7 while running on alternative fuel; continued operation may increase emissions and risk catalyst damage. Possible drivability loss; further diagnosis required.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours