Service engine soon light

[shaamonaz]

I have a 99 Tahoe the service engine soon light come on and the dealer told me I needed a canister vent valve. I brought and replaced the part and the light went out then the next day it came back on. The dealer also said that I should change my O2 sensors and don't put high octane gas in my car. Do anyone have any ideas on what I should do? I did not get the code cleared out of the system so I wonder if that is why the light came back on. Please help because the O2 sensors are alot of money.

[bcopeland]

These things are usually very dependable. Most times, my codes came on because the fuel cap was old and needed replacing or it was not tightened when I let my son fill up the vehicles.

[Bob Oney]

My "service engine light soon" came on Saturday when I had to put the pedal to the metal to pass a car, and I had a full load of passengers and lots of weight in the back. It remained on until I put some gas in it this morning, and it went out. The day before, I took the gas cap off and put it back on to see if that would make the light go off, but it didn't. I'll wait until it comes back on again before having it analyzed.

[GMMerlin]

Originally Posted by Bob Oney

My "service engine light soon" came on Saturday when I had to put the pedal to the metal to pass a car, and I had a full load of passengers and lots of weight in the back. It remained on until I put some gas in it this morning, and it went out. The day before, I took the gas cap off and put it back on to see if that would make the light go off, but it didn't. I'll wait until it comes back on again before having it analyzed.

The PCM has stored a code related to the problem. Even though the light has gone out, the code is still there.

[bcopeland]

Bob - Just because you replace the gas cap, it does not mean the light will go out! You must have the codes read and erased.

[Bob Oney]

Originally Posted by bcopeland

Bob - Just because you replace the gas cap, it does not mean the light will go out! You must have the codes read and erased.

Well, yesterday I took it to my favorite garage for an oil change and they put the machine on it and it reported NO codes. I think it has something to do with putting gas in it. Perhaps the fuel pump is going bad. The gas guage is a little tricky, too. It will read about half-full for a suspiciously long time; then after restarting, it will read about 1/8th full. BTW, the Yukon has 110,000 miles.

[sTUNNA]

I just got the same problem today. I'm not sure why but Im guessing by the way I was driving. When I got out (first turn) I revved it max rpm, which isn't really a problem, cause I've done it many times, then after that I noticed the service light was on. Anyone got any suggestions? Oh yeah its a 03 Denali.