Failed ignition coil pack. Worn spark plug. Blocked or leaking fuel injector. Compression loss. Carbon buildup on intake valve (direct injection engines).

Which cars are affected by P0303?

P0303 is most commonly reported on Ford, Vauxhall, BMW, Audi, Toyota vehicles, but can appear on any make.

← All fault codes

P0303

High severity

Cylinder 3 Misfire Detected

A misfire has been detected specifically in cylinder 3. This isolates the fault to components serving that particular cylinder, making diagnosis more targeted than a random misfire code.

Get a full AI diagnosis for your vehicle

Enter your reg plate and fault code — Velocito.ai cross-references technical databases, MOT history, manufacturer recalls, and known fixes to pinpoint the exact cause.

Diagnose P0303 free3 free searches — no card required

Common causes of P0303

1Failed ignition coil pack

2Worn spark plug

3Blocked or leaking fuel injector

+2 more causes

Get all causes ranked by likelihood for your specific vehicle — plus the cheapest confirming test for each.

Diagnose P0303 free

Commonly affected vehicles

FordVauxhallBMWAudiToyota

P0303 can appear on any vehicle — these are the makes where it is most frequently reported.

Full diagnosis report

Most likely cause for your vehicle

Based on your vehicle's make, model, year, and MOT history, the most probable cause is identified and ranked by likelihood.

Confirming diagnostic test

The cheapest test to confirm the root cause before replacing any parts — saving time and money on unnecessary work.

Recalls & technical bulletins

Manufacturer recalls and TSBs checked automatically for your specific vehicle, so nothing gets missed.

Unlock the full report

Enter your reg plate to get causes ranked for your specific vehicle, confirming tests, recall checks, and known fixes.

Try 3 free searches

Stop guessing. Start diagnosing.

Enter your reg plate and P0303 — get a full diagnostic report in seconds.

Try 3 free searches

Related fault codes

P0171Medium

System Too Lean (Bank 1)

P0300High

Random/Multiple Cylinder Misfire Detected

P0420Medium

Catalyst System Efficiency Below Threshold (Bank 1)

P0172Medium

System Too Rich (Bank 1)