Code P0305 2009 Pontiac G8 Base

2009 Pontiac G8I have cylinder 5 misfire code p0305 on my 2009 Pontiac G8 base 3.6L V6. I’ve tried messing with it. I switched the spark plugs and tested the coil pack on cylinder 5, the test showed it was fine. I had a “professional” shop look at it and they told me it seems like the head was cracked and the piston in cylinder 5 was burned. Which is impossible because my car does not over heat at all and turns on just fine. It runs pretty decent besides the misfire no leaks or anything! What could it be?


The P0305 code means that cylinder 5 is misfiring and or is randomly misfiring. Start by checking for intake leaks an if no leaks are found the next step is to replace the spark plugs on cylinder 5. Most common cause would be a faulty coil. Try swapping it with a different cylinder, clear the codes and see if the issue follows the coil. Don’t rule this out just because it passed your test. See if it passes mine. If the problem persist more tests needs to be done to diagnose problem, see “Possible Causes”

Pontiac Code P0305 – Cylinder 5 Misfire Detected

Possible causes

– Faulty spark plug 5
– Clogged or faulty fuel injector 5
– Faulty ignition coil 5
– Fuel injector 5 harness is open or shorted
– Fuel injector 5 circuit poor electrical connection
– Ignition coil 5 harness is open or shorted
– Ignition coil 5 circuit poor electrical connection
– Insufficient cylinder 5 compression
– Incorrect fuel pressure
– Intake air leak

Code P0305 Description

First of all, when a misfire occurs, engine speed will fluctuate. In addition, if the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring.