What does code P0305 mean on a Pontiac and is it safe to drive?
P0305: Cylinder 5 Misfire Detected. Here's what it means on your Pontiac, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
What this code means
Misfire on cylinder 5—present on V6, V8, and inline-5 engines only. On V6 engines, cylinder 5 is sometimes harder to access; factor labor into repair estimates.
Common causes for your Pontiac
- Fouled spark plug
- Failed ignition coil
- Leaking or clogged injector
- Low compression from valve or ring wear
Symptoms
- Check Engine Light
- Engine shaking or rough idle
- Power loss under acceleration
Typical fixes
- Replace spark plug and coil on cylinder 5
- Test and replace injector if needed
- Compression and leak-down test
Repair cost range
For a Pontiac, repairs for P0305 often fall between $150 and $1000, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
Known issues on Pontiac
Pontiac G8 and GTO LS2 V8 P0305 is uncommon on these extremely durable engines. When it occurs, a failed COP coil or fouled spark plug is the typical cause. On the 3.8L supercharged Grand Prix, P0305 is more common from coil boot cracking due to heat near the supercharger.
Most commonly affected models