P0305: Cylinder 5 Misfire Detected
Cylinder 5 is misfiring, which means your engine has at least five cylinders and one of them is not burning fuel properly.
What P0305 means
P0305 only appears on engines with five or more cylinders, which usually means a V6 or V8. The misfire monitor uses crank speed and the firing order to tie the missed power stroke to cylinder 5. On many front wheel drive V6 engines, cylinders 2, 4 and 6 or 1, 3 and 5 sit on the rear bank, tucked under the intake plenum against the firewall. That location matters for your wallet: plugs and coils there can take an hour or more of extra labor. The causes are the same ones behind any single cylinder misfire, a coil, plug, injector or compression problem, but shops are careful to confirm before tearing into the intake. They use a scan tool with misfire counters, a coil swap if access allows, and a compression test. Fix it before the misfire damages the catalytic converter on that bank, which may set a P0420 or P0430 next.
Common symptoms
- Check engine light on, or flashing when the misfire is bad
- Rough or shaky idle
- Hesitation or jerking when you accelerate
- Loss of power, especially going uphill or merging
- Worse gas mileage
Most common causes
- Failing ignition coil on cylinder 5
- Worn spark plug, often the hardest to reach on V6 engines
- Leaking intake plenum gasket
- Faulty or clogged fuel injector
- Coolant or oil intrusion into the cylinder
- Low compression from valve wear
What to check yourself first
Look up where cylinder 5 sits on your engine; on many transverse V6 engines it is on the rear bank against the firewall. If it is easy to reach, swap its coil with a front bank coil and watch for the code to move. If it is under the intake, leave it to a shop.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace ignition coil | $238-$320 | On many V6 engines the rear coils sit under the intake plenum, which adds labor. |
| Replace spark plugs | $288-$399 | Rear bank plug jobs cost more because the plenum often has to come off. |
| Replace intake manifold gasket | $683-$834 | If the plenum or intake gasket is leaking near that cylinder. |
| Replace fuel injector | $768-$953 | Replace after a failed injector test. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0300 Random/Multiple Cylinder Misfire Detected
- P0306 Cylinder 6 Misfire Detected
- P0304 Cylinder 4 Misfire Detected
- P0174 System Too Lean (Bank 2)
- P0430 Catalyst System Efficiency Below Threshold (Bank 2)