P0301 to P0308: a misfire on one specific cylinder
The same fault as P0300, but the car has isolated it to one cylinder. The number in the code tells you which. If the light is flashing, slow down and have it looked at quickly.
Can you keep driving?
Steady light: yes, in the short term. Flashing: drive as little as possible.
What the code means
The last digit is the cylinder number: P0301 is cylinder 1, P0304 is cylinder 4.
Because the fault is isolated, it points to something specific to that one cylinder.
Common causes
- A worn spark plug on that cylinder
- A failing ignition coil
- A problem with the fuel injector
- Low compression, which is the expensive version
What to do now
- Note the code number. That is half the diagnosis.
- If the light is flashing, slow down.
- Ask the shop to swap the coil and plug with a neighbouring cylinder and re-read. If the code moves, you have found the part.
What people often get wrong
That the code points at a faulty part. It points at a cylinder. Which part is failing in that cylinder still has to be found.
When the car must go to a workshop
If the fault does not move when the coil is swapped, it can be compression or an injector, and that needs measuring.
Read next
- P0300: misfire on more than one cylinder
- Your check engine light isn't random
- P0171: system too lean
This page is general information and does not replace a professional assessment. Symbols, codes and behaviour vary between makes. Always check the handbook for your own car.
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