Trouble code
P0303
Cylinder 3 Misfire Detected
What P0303 means
Cylinder 3 is misfiring.
Symptoms you may notice
- Rough idle
- Power loss
- Flashing check engine light
Common causes, cheapest first
- Failed ignition coil
- Worn spark plug
- Injector fault
- Low compression
Before you buy anythingCoil swap test first, plug inspection second, compression test last. Work cheapest to most expensive.
What to do next
- Confirm the code with your own scan tool, or have it read free at a chain parts store.
- Decode your VIN so you know your exact engine and build date.
- Work down the causes above from cheapest to most expensive.
- Search NHTSA for a recall or service bulletin covering this symptom on your vehicle.
- Read the ignition buying guide before ordering.
P0303 is a generic OBD-II code, standardized across every make and model sold in the US from 1996 onward. The meaning is the same on any vehicle; the specific part and its location are not.
Parts
Parts commonly needed for P0303
These go to Amazon. We earn a commission if you buy, at no extra cost to you — see our affiliate disclosure. Which one you actually need depends on diagnosis — read the note above first.
Confirm fitment against your VIN on the listing page before ordering. A part that matches your year and model can still be wrong for your build date or engine code.