2006 GMC P0305: What It Means & Is It Safe to Drive?
P0305 on the 2006 GMC: Cylinder 5 Misfire Detected. Here's what it means, what usually causes it, what repairs typically cost, and whether it's safe to keep driving.
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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 on the 2006 GMC
- 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 2006 GMC, repairs for P0305 typically fall between $150 and $1000, depending on the root cause and labor rates in your area.
Known issues on GMC
GMC Sierra 5.3L P0305 is an AFM deactivation cylinder—lifter collapse is the primary suspect on high-mileage trucks. On the 4.2L inline-six Envoy, P0305 cannot occur (only 6 cylinders active). On the 5.3L, an AFM delete kit prevents recurrence.
Most commonly affected models
Sierra 5.3L AFM 2007–2014Yukon XL 5.3L 2007–2014Envoy 4.2L I6 2002–2009