Cylinder 3 misfire.
P0303 — also written PO3O3, P 0303, 0303 — is the OBD-II code for cylinder 3 misfire detected. Same code, same fix: this page covers every spelling of it.
Cylinder 3 isn't pulling its weight, usually because the spark’s gone weak or the injector's blocked. Very common on the VW Group 1.2 TSI and Vauxhall 1.4 units.
P0303 is a ignition fault code, typically costing £30–£800 to put right in a UK garage.
What P0303 actually feels like to drive
- The engine 'kangaroos' or hesitates when you’re pulling away from a roundabout.
- The car feels like it’s 'chugging' or running on three cylinders when idling at traffic lights.
- The EML (Engine Management Light) starts flashing when you’re pushing it up a steep hill or overtaking.
- A heavy smell of unburnt petrol coming from the exhaust pipe at cold start.
- The car struggles to 'pick up' from 2,000 RPM in 4th or 5th gear.
What causes P0303?
- Spark plug
- Coil
- Injector
UK vehicles that throw P0303 most often
- Vauxhall Corsa D/E 1.2 & 1.4 (A12XER/A14XER) 2009-2018
- Ford Fiesta/Focus 1.0 EcoBoost (M1DA) 2012-2020
- Volkswagen Golf/Polo 1.2 TSI (CBZA/CBZB) 2010-2015
- Vauxhall Astra J 1.4 Turbo (A14NET) 2010-2015
- BMW 1 Series (F20) 116i/118i (N13 engine) 2011-2015
- Nissan Qashqai 1.2 DIG-T (HRA2) 2013-2018
How P0303 is fixed
- Plug & coil replacement
The P0303 misdiagnosis that wastes money
I’ve lost count of how many times I’ve seen brand-new spark plugs and coils thrown at P0303 on Vauxhalls and Fords, only for the car to come back the next day with the same limp mode. People forget that on the Astra J and Insignia, the coil pack is one big rail—you can't just swap one cylinder. The real 'gotcha' we see in the workshop is carbon buildup on the valves or a failing injector. If the plug looks wet with petrol, look at the coil; if it’s bone dry and white, your injector’s probably given up the ghost.
What a UK garage should charge for P0303
For a basic Spark Plug swap, you’re looking at £30-£60 using NGK or Bosch. If the Coil Pack is shot, an independent like me will charge between £120 and £220 for the part and 30 mins labour. If it’s a Bosch injector on a modern direct-injection engine, that can climb to £450-£600. Be warned: a main dealer will easily double these prices with 'diagnostic fees' often starting at £120+VAT before they even pick up a spanner.
P0303 repair cost in the UK
Most P0303 repairs land between £30–£800 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Bob's tip on P0303
Before you let a garage sell you a full set of injectors, ask them to do a 'leak-back test' and a compression check. If it’s a Ford EcoBoost, insist they check the coolant level too—cylinder 3 is often where the head gasket fails first, and it 'washes' the spark plug, causing the misfire. To save yourself a packet, ask if they can swap the cylinder 3 coil with cylinder 1. If the code moves to P0301, it’s just the coil. If it stays on P0303, you’ve got a deeper mechanical or fuelling issue.
Can you drive with P0303?
Drive gently.
Urgency: high.