OBD2 Code P0391: Misfire / Ignition System
Misfire detected.
Detected Root Component
Powertrain Component
Observed Symptoms
- Engine light on (MIL/Check Engine)
- Rough or unstable slow motion
- Loss of engine power
- Abnormal engine vibrations
- Engine stalling
Possible Causes
- Worn spark plug
- Defective ignition coil
- Clogged or faulty injector
- Vacuum leak
Tools Required
Interactive Diagnostic
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Parts likely to be the cause (Moteur (général))
Moteur (général)
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Frequently asked questions about code P0391
What does code P0391 mean? ▾
OBD2 Code P0391: Misfire / Ignition System. Misfire detected.
What are the symptoms of code P0391? ▾
Code P0391 may cause: Engine light on (MIL/Check Engine), Rough or unstable slow motion, Loss of engine power, Abnormal engine vibrations. The intensity of these symptoms varies depending on the vehicle and driving conditions.
What causes code P0391? ▾
The most common causes of code P0391 are: Worn spark plug, Defective ignition coil, Clogged or faulty injector, Vacuum leak. A proper OBD2 diagnostic will pinpoint the exact cause.
Is it serious to drive with code P0391? ▾
Yes, code P0391 is critical (Critical). Avoid driving and consult a professional promptly to prevent major damage.
How do I fix code P0391? ▾
Start by reading the code with an OBD2 scanner, then follow the interactive decision tree on this page. Priority causes to check: Worn spark plug, Defective ignition coil, Clogged or faulty injector, Vacuum leak. Difficulty: Medium · Estimated time: 30-60min.