Fault code

P0303 fault code.

This code comes up with one known fault.

Generic code

Code type

Engine and drivetrain

System

Misfire on cylinder 3

The engine control unit detects a misfire from the momentary slowdown of the crankshaft, and tied this one to cylinder 3. An ignition coil, a spark plug, an injector or a leak can all cause it. The repair is often a new spark plug or a new ignition coil.

The code tells you what the control unit measured, not which part has failed. The same code has several possible causes.

Which known faults it comes up with

1.0 TSI: an injector that will not seal, fuel leaking into the cylinder

expensive

The injector does not close fully, and with the engine standing fuel drips into the cylinder. The symptoms are hard, long cranking (mostly after standing for a while), smoky first minutes, a hesitant idle, and dilution of the engine oil: the oil level goes higher, it smells of petrol, and the diluted oil lubricates worse. It shows up on cars built between 2018 and 2020.

What to check

Start it cold after standing for a while: several seconds of cranking and blue-white smoke are suspect
Pull the dipstick: a level rising above MAX and a petrol smell indicate dilution
Smell the oil filler: a petrol smell means fuel has got into the oil

2 more steps in the write-up

Information, not an expert opinion

We write the descriptions, and we put the source next to them. A person reviews them before they go out. They are still information, not a technical expert opinion.

A fault on the list does not mean the car you are looking at has it.
A fault missing from the list does not mean the model is fault-free. Write-ups are made model by model. Not all of them are done.
You decide whether to buy. This is no substitute for an inspection. That needs a workshop and a history check.

Details in the terms