P0308 fault code: Cylinder 8 Misfire Detected
Driveability guidance is not available for this code — treat as do not drive until checked.
Can I DIY?
Professional-only boundary. You may confirm cylinder 8 and the lamp state; coil or plug work is not published for this code.
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 P0308
Do not drive. The engine computer has detected that cylinder 8 is misfiring. A flashing engine management light with a shake means stop; even a steady light can send unburnt fuel into the catalyst as a consequence.
Take these reviewed, code-specific details with you. They help the garage confirm the fault without turning this page into a repair procedure.
- Cylinder 8 Misfire Detected: Registration number
- Cylinder 8 Misfire Detected: Exact code P0308 and any other misfire or coil codes
- Cylinder 8 Misfire Detected: Whether the engine management light is steady or flashing
- Cylinder 8 Misfire Detected: Whether the car judders, shakes at idle, or feels down on power
- Cylinder 8 Misfire Detected: Whether misfire counts stayed on cylinder 8 if your scanner showed them
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.
What does P0308 mean?
P0308 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 8 Misfire Detected”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.
Will P0308 fail an MOT?
An illuminated engine management light is a Major defect at MOT (automatic fail) until the fault is repaired and the light stays off. A misfiring engine can also fail the 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
Related fault codes
P0308 — quick answers
Is it safe to drive with P0308?
Do not drive. Driveability guidance is not available for this code — treat as do not drive until checked.
Will P0308 fail my MOT?
An illuminated engine management light is a Major defect at MOT (automatic fail) until the fault is repaired and the light stays off. A misfiring engine can also fail the 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.