Engine Light

[HumanZoom]

Hi! I am pretty new to this board, so I don't know if this has been covered or not. I have a 2003 GMC Sierra 1500. However, yesterday the engine light came on out of the blue. I looked in the owner booklet and it gave a few possible suggestions. One being modifcations to exhaust (or several other things which don't apply to me). Well, I recently had a custom dual exhaust system with two FlowMaster Racing mufflers, however that has been more like a month and a half ago and like I said, this light came on yesterday. So I am thinking that it isn't the exhaust. Other possible things: fuel cap not on tight enough (double and triple check...not a problem) or bad fuel. That is the only thing I could think that might have caused it (since I did pick a different station that I don't always go to and their pump seemed to act a little odd), although that was more than a week and a half ago and as I have mentioned twice before that light just came on. I refilled the tank again today (had a little more than half a tank) with the station I usually fill it with. I realize this may take a few tank fulls to clear out the bad gas (if any). However, I was wondering: could the bad gas have damaged my fuel tank or other fuel components and should I get this looked by a dealer (I really don't want to go to a dealer and pay that money for something like bad gas). Also, I thought I would mention that I have not suffered any lack of performance. Still sounds, drives, starts, shifts, etc. the same. Is this just a case of bad gas....or something more?  ???

 

Thanks -HZ

[Shaners]

Your dealer should be able to read the code and tell you the problem.  It should be covered under warranty.

 

If you don't want to take it to the dealer, then places like AutoZone will read the code for free too...

[Black02Silverado]

My 02 light came on also and I had Onstar run a check. I got the codes and posted them on here. It was a whole bunch of stuff but boiled down to water in the gas. My light came on just after I refueled and in about 20 miles of driving. It cleared it's self after another 20 miles of driving. I live out in the country. The dealer told me to bring it in but when the light went out I had OnStar recheck and there were no codes listed in my system, so I just opped to not take it in and went with the bad gas. So far that has been over a month ago and it is running fine with no light.  I must say OnStar was worth the money then and I feel still is. IMO  

 

Like Shanners said you can have Auto Zone check it for you.

 

[HumanZoom]

Great, thanks for your help. Unfortunately, I didn't get OnStar, but I am leaning toward the bad gas theory. As of today it was still on, but I'm going to wait a little bit to see if it will clear itself up (maybe after another refill of the tank). If not I may take to the dealer then. Thanks again for all your help Shaners and Black02Silverado.

 

-HZ

[silverado3500]

Assuming you did not mess with your 02 sensors or your cats, your exhaust system is not the cause of your service engine loght.  I'd probably opt for the gas theory, but take it to the dealer to be sure as it is free under warranty!