P0305 and P0305PD Fault on 2006 Colorado I5 - How to Diagnose Coil or Injector?

Model: Colorado Fault Code: P0305 Posted: 2011-01-30 18:43

I own a 2006 Colorado with a 5.0L V8 engine and am consistently receiving diagnostic trouble codes P0305 and P0305PD. I've already replaced the spark plug, which has improved engine performance slightly—though a noticeable stumble still occurs when decelerating from higher RPMs. I've also inspected the air filter and confirmed it is not clogged or excessively dirty. Despite these efforts, the issue persists. My next step is to determine whether the problem lies with the ignition coil or fuel injector for cylinder 5. What is the most effective method to test either component? Any recommendations or troubleshooting steps would be greatly appreciated.