P0306 fault code: Cylinder 6 Misfire Detected
Driveability guidance is not available for this code — treat as do not drive until checked. If the engine management light flashes or the car judders, stop and arrange recovery.
Can I DIY?
Professional-only boundary. Confirm P0306 and whether the light flashes; do not swap coils or plugs for cylinder 6 from this page.
This is the conservative boundary from the reviewed code record. This page has no frozen site-wide safety grade, so it does not publish a repair route.
What to tell the garage about P0306
Do not drive. Cylinder 6 is misfiring. If the engine management light flashes with judder, stop. Unburnt fuel can overheat the catalyst. A four-cylinder engine should not normally store P0306 — confirm the scan at a garage.
Take these reviewed, code-specific details with you. They help the garage confirm the fault without turning this page into a repair procedure.
- Cylinder 6 Misfire Detected: Registration number
- Cylinder 6 Misfire Detected: Exact code P0306 and any other misfire or coil codes
- Cylinder 6 Misfire Detected: Whether the engine management light is steady or flashing
- Cylinder 6 Misfire Detected: Whether the car judders, loses power, or feels normal
- Cylinder 6 Misfire Detected: Engine layout (four-cylinder versus six or more) if known
Never idle in a closed garage to read codes — an open door is not enough. CO is odourless and can kill. Run diagnostics in open air. Headache or nausea with exhaust smell: get fresh air and stop.
Never open a hot coolant cap — pressure can scald you. Exhaust and catalytic converter get hot enough to burn and ignite debris. Stay clear of electric fans; they can run after shut-off.
What does P0306 mean?
P0306 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P03xx block, which covers ignition system and misfire. The stored description is “Cylinder 6 Misfire Detected”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.
Will P0306 fail an MOT?
An illuminated engine management light is a Major defect at MOT (automatic fail) until the misfire is repaired and the light stays off. A misfiring engine can also fail the exhaust emissions test.
Before booking your test, check what usually fails on your car: see our MOT pass rates by make and model, built from 33.1 million DVSA tests.
Related guides
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P0306 — quick answers
Is it safe to drive with P0306?
Do not drive. Driveability guidance is not available for this code — treat as do not drive until checked. If the engine management light flashes or the car judders, stop and arrange recovery.
Will P0306 fail my MOT?
An illuminated engine management light is a Major defect at MOT (automatic fail) until the misfire is repaired and the light stays off. A misfiring engine can also fail the exhaust emissions test.
Fault-code identifiers are standard diagnostic facts. Their explanations and diagnostic guidance on this site are original editorial summaries, not reproduced SAE wording. MOT defect rules reflect the DVSA MOT inspection manual (2026). This page is general guidance for UK drivers, not a substitute for a professional diagnosis.