P0302
PowertrainCylinder 2 Misfire Detected
Cylinder 2 specifically is misfiring. The ECU's misfire counter has logged enough missed combustion events on that one cylinder to set a code.
ⓘ Information only. This page provides general educational information about fault code P0302. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0302 mean?
P0302 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cylinder 2 Misfire Detected.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Rough idle that often clears slightly when revs come up
- • Engine warning light, flashing if the misfire is severe enough to threaten the catalytic converter
- • Loss of power, most noticeable on hills or pulling away from a stop
- • Occasional smell of unburned petrol from the back of the car
- • Small juddering vibration through the seat or steering wheel at idle
Possible causes
Causes commonly associated with P0302, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Worn or fouled spark plug in cylinder 2 (especially on cars overdue a plug change)
- 2. Failed ignition coil pack on cylinder 2
- 3. Blocked or sticking injector for cylinder 2
- 4. Damaged HT lead on engines that still use them
- 5. Vacuum leak local to cylinder 2's intake runner
- 6. Less commonly, a compression fault: worn valve, damaged piston ring, or failing head gasket on that cylinder
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Pull cylinder 2's spark plug and inspect it. Oil-fouled, carbon-fouled, or worn-down electrodes tell their own story
- 2. Swap cylinder 2's coil with one from a healthy cylinder, clear the code, and drive a few miles. If the misfire follows the coil to the new cylinder (e.g. P0303 appears), the coil is the fault. This is faster and cheaper than guessing
- 3. Same swap test with the injector if accessible, some engines make this difficult
- 4. Run a dry compression test on cylinder 2. Significantly low compared to the others points to a mechanical issue
Common questions about P0302
Should I just replace all four plugs at once? +
If the plugs are all the same age and the car has done over 30,000 miles since the last change, yes, it's better practice. A worn cylinder 2 plug usually means the others aren't far behind. If the car was plugged recently and the others look fine, you can replace just the one.
If the warning light is flashing, can I drive home? +
A flashing light specifically means the misfire is bad enough to risk the catalytic converter, so the rule of thumb is to stop as soon as it's safe and not drive further. Continuing can cost you a £600-£1,500 cat. If it's only a steady light, a short drive to a garage is usually fine, but always confirm with a mechanic.
Why does my engine smell of petrol? +
Unburned petrol from the misfiring cylinder is going down the exhaust. That's also why a flashing light matters, hot unburned fuel hitting the catalytic converter destroys it.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →