Code P0305 Cylinder #5

Ger8mm · September 15, 2018

I have a 2015 GMC Sierra 1500 All-Terrain, BlackBear Tuned, V4 Delete, run Mid-grade fuel.

This is the second time its happened within a few months, different cylinder but the same side the dealer repaired. I should still be under warranty for this fix too but can anyone else relate to this issue? Is it the tune? could the V4 disabled make the problem worse? I guess when my warranty is up and it fails again I heard there is an AFM delete you can install that should fix this issue.

snailtrax · September 15, 2018

I had that code pop up om my 2014. it was a loose spark plug wire on the coil end. Touched it and it fell off. Reconnected it till it clicked in place and all was good.

newdude · September 15, 2018

Cylinder 5 is not AFM. Cylinders 1, 4, 6 and 7 are the AFM cylinders. 2, 3, 5 and 8 are non AFM cylinders, and do not have AFM hardware, just regular lifters. Delete/Range won't help a cylinder 5 miss.

Seen plenty of bad DI fuel injectors on these 2014+up trucks that cause come and go misfires. Loose plug wires is another common deal.

Ger8mm · September 16, 2018

On 9/15/2018 at 3:08 PM, newdude said:

Cylinder 5 is not AFM. Cylinders 1, 4, 6 and 7 are the AFM cylinders. 2, 3, 5 and 8 are non AFM cylinders, and do not have AFM hardware, just regular lifters. Delete/Range won't help a cylinder 5 miss.

Seen plenty of bad DI fuel injectors on these 2014+up trucks that cause come and go misfires. Loose plug wires is another common deal.

ThanksI did not know this, I will find out tomorrow but there is a loud clicking noise when it's running.

Ger8mm · September 16, 2018

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Ger8mm · September 16, 2018

newdude, I definitely owe you a Beer now, The spark plug wire was loose.

Thanks a ton for the info and not a trip to the dealer.

Parrish Mooneyham · January 13, 2020

Hey guys, I have a 2014 Silverado 1500 LT double cab and at about 90,000 miles I got the first p0305 code, I have replaced the coils the wires and the plugs. Now at about a 115,000 miles the engine light flashed as I was coming home and went off while while driving. I checked after I got home and it was the same code, the p0305. I am crossing fingers and hoping that the injector on cylinder 5 is the only issue. I have ordered all new injectors for all 8 cylinders of course I had to buy aftermarket because OEM is too expensive. I wanted to put this on record just show another buyer of GM having issues with this. It may take another 20000 miles or more before I figure out if something else is going wrong or if the injector fixed the issue. So it may take awhile for me to reply back and if this fix the issue or not. I'm also replacing the plugs just to be safe as well. If this happens again, my only option is to take it into the dealership or my local mechanic if you'd turns into a rocker or when a electronic pcm programming issue. I just hope my cats aren't screwed up. Those are new as well as of about 96k cause I believe this p0305 issue burned one side out, so I had both replaced at that time as well.

Parrish Mooneyham · January 14, 2020

Ok guys just a quick update, I called my shop guys about the issue, they stated for 75 bucks, they would do injector tested, cylinder compression test AND a few other things,. If nothing is found, they would swap cyl 5 injector with another non AFM cylinder and then I'll run it for a while and see if the code shows back up and is so if it's the new swapped cylinder or same old cylinder. I guess from there well see, I'll report back if the shop find anything and what was done. I'm crossing fingers that's it's just an injector issue, I really don't want to have to deal with an engine replacement as that will be out of my pocket. Hehehe.

Ozer · January 14, 2020

You sure they will swap an injector? You need to remove the intake manifold to get to the injectors, at that point might as well just install a new one vs swapping it.

If you have some DIY knowledge you can swap spark plugs/coils/wires around yourself and even a compression test isn't hard with a kit but for 75 bucks, it may not be worth the hassle.

Report back.

Parrish Mooneyham · January 15, 2020

Hey Ozer, they STATED they were going to do that, but after they ran a compression test and indicated the compression was VERY good on all 8 cylinders, i had a discussion with the tech. Because the fact that compression is good and wires, plugs and coils are 'good'. The sporadic issue comes with a few various possibilities.. the easiest being the injector is bad. The other not easy part is there is possibly valve leak or something more internal with the engine as this is so sporadic in nature and the fact that i'm still paying on this AND may have a pretty expensive repair coming for anything internal engine related, prompted me to trade in the truck and upgrade to a 2020 Silverado LT Double Cab.. I know!! I know!! possibly back to the same issue. I'm crossing fingers that this one will last. The engine a L84 5.3 which my current is a L83 5.3. I just hope they worked out all the bugs on this one being 6 years later. So I won't know what the fix will be as I have new truck (well it is a 'retired loaner' from the dealership with 3110 miles already). This was the only way I could a new truck with same payments. I just rolled over the equity from my current truck as it was going to be pay off this year. So i'm sorry guys if I caused any grief. But I just wanted out something that could turn potentially costly in the very near future. By the way, the new truck has a 100k bumper to bumper for only like 10 bucks extra a month. So I feel pretty good about that part. Good luck on all your other endeavors.