Draft guidance: awaiting Claude spot-check, qualified-mechanic review and named-editor approval. Do not use a fault code alone to replace parts.

P0302: Cylinder 2 misfire detected

The engine control unit has recognised repeated or significant misfire activity associated with cylinder 2.

What P0302 means

The engine control unit has recognised repeated or significant misfire activity associated with cylinder 2. The code says where uneven combustion was detected, not which part should be replaced. The physical position of cylinder 2 must be checked against the manufacturer's engine layout.

Can I still drive?

Treat P0302 as urgent if the misfire is active. A flashing engine-management light is the key stop boundary because a severe misfire may damage the catalytic converter. Do not continue driving if the light flashes or turns red, the engine shakes heavily, power falls sharply, the car stalls, or there is smoke, overheating, a fuel smell or an abnormal mechanical noise. If the light is steady amber and the engine remains smooth, with no leaks, smells or temperature warning, drive only gently and for the minimum distance needed to reach a nearby garage. Avoid motorways, towing, steep-load driving and attempts to clear the fault with high engine speed.

Symptoms

Illuminated or flashing engine-management light
Rough idle or vibration through the vehicle
Hesitation, flat spots or reduced power
Judder that becomes worse under load
Difficult starting or stalling at idle
Increased fuel consumption or exhaust smell
No noticeable symptom if the event was intermittent

Common causes

Cylinder 2 spark plug worn, fouled, cracked or incorrectly gapped on a petrol engine
Weak ignition coil, coil boot or HT lead serving cylinder 2
Cylinder 2 injector restricted, leaking or electrically faulty
Loose, corroded or damaged injector or ignition wiring
Air leak near the cylinder 2 intake runner or injector seal
Loss of compression through valve leakage, ring wear, head-gasket failure or valvetrain damage
Oil, coolant or carbon contamination in that cylinder
A shared fuel-pressure, air-metering, timing or engine-management problem, particularly when other codes are stored

Safe first checks

Record all stored and pending codes, freeze-frame data and scanner misfire counts before erasing anything.
Use vehicle-specific information to locate cylinder 2; do not infer its position from the front or left side of the engine.
Once the engine is cold and switched off, inspect accessible connectors, wiring, intake hoses and the plug-well area for looseness, damage or moisture.
Check oil and coolant levels and look for a new leak. Never remove the coolant cap while hot.
Compare the fault with recent work; disturbed connectors, new plugs or a loose intake hose can all matter.
Leave running-engine ignition checks, fuel-rail work and compression testing to a competent person with the right equipment.

Typical UK fix cost

A sensible provisional allowance is £100–£450 for diagnosis and a typical plug, coil, local wiring or single-injector repair. Difficult access, direct injection, diesel components or premium parts may increase the price. Mechanical compression, timing, cylinder-head or catalytic-converter repairs can exceed £600–£2,500. Treat this as a broad editorial estimate requiring a current written quote and human review.

Related models

This is a generic OBD-II code used across many makes and models. The exact test thresholds, component layout and repair route vary by engine and manufacturer, so check vehicle-specific technical information before ordering parts.

Related fault codes

Sources

A diagnostic trouble code identifies a system or circuit to investigate. It does not prove that a named part has failed. Preserve freeze-frame data and seek a vehicle-specific diagnosis before clearing the code.