[acampbell25]

I'm really hoping I can get some help with this issue. Basically whats going on. So I bought this denali about 3 months ago and really enjoy it. However it has had its fair share of issues. The most recent is a p0308/p0300 code. The code the p0308 code poped up one day while out driving to lunch roughly around the time the truck was running at operating temperatures (didn't notice any change in how it drove/ran). So after work I go to drive home for the weekend (5hrs) and stop at a gas station to get some gas. Filled up and turned my truck on and the light is off. Take it home have the town mechanic hook it up to a snap-on scanner saturday morning and he tells me its reading a p0300 code but the check engine code isn't on except for when you turn the key to accessory. So I figured well I may as well change the plugs so I did and the truck ran great half way back up to work, but then I noticed the mpg drop down a slight bit but no check engine light. So today I leave work to travel to another site and half way here the check engine light comes on( didn't run rough or any thing). I stopped and got wires so that I could change them when I get a chance this week. Well once I get out of the parts store and go to start my truck it fired right up but quickly died and I got a service air bag light. Tried to start it 2 more times with the same results (sab light) then on the last try it started just fine. drove across the street and noticed the idle was a little low so went in to collect my thoughts and get something to drink. Come out and it starts just fine and ran fine w/light on the whole way here (50ish miles). I don't have alot of time to chase problems so I'm thinking about taking it to a mechanic. Any last ideas on what it could be. Also should I take it to a regular mechanic shop or to a gm dealer incase it is a computer issue and needs reprogrammed.?

Its a 2007 Sierra Denali
120k miles
volant intake
aftermarket headers

 

[FiestyZ71]

Was the truck tuned for the headers? Do u still have cats?

 

[2005_Silverado]

check your grounds and the battery

 

[acampbell25]

sorry I should have included that kind of information. The truck was tuned for the headers and it still has both cats.

Probably not a bad idea to check the battery that could be where my service seat belt light came from.

 

[Chitter]

What gas did you use? I always use Chevron or 76 and never have problems. I helped some friends one day and they filled my tank. Stupidly I let them fill it at Arco! 20 minutes later I was getting check engine light and misfire codes. Also a bad o2 censor code. I put some octane booster in and reset light. Filled up with premium next trip and no issues since. Not sure what your air bag light is but my guess is the misfire is bad gas, maybe just a bad batch.

 

[acampbell25]

honestly I use 2 different gas stations but I havent had it long enough to put to many tanks through it. I use quick trip and then a little local gas station. It has had 91 ran through it since I've had it. I had to put about 10 gals of 87 in it once to get to a gas station that had 91 and then again last week same deal. The first time i put 87 in it then later put 91 in it and half way home i got the traction control message pop up. however after replacing the plugs I got 18.x on the way back to work this weekend but I noticed half way there it started to drop down to high 15's - mid 16's. this all happened after driving through a heavy rain storm. So i'm not sure if something that wasn't supposed to get wet got wet or what.