Unhooking the battery cable overnight (or even for 30 minutes) will reset the computer in some cars. I'm not sure, however about the Envoy. You might try it, but BE SURE your radio is not in the "anti-theft" mode or the system won't recognize it when the battery is reconnected.
You may also have a slightly tight new alternator, which could be putting a slight drag on the engine and causing the computer to screw up. I'd try the cable thing, just be sure it won't mess up your security stuff. I've unhooked my 2003 GMC Envoy's battery (to replace the battery) and it caused no problems at all.
The battery is all I've ever replaced on mine. This is one of the best vehicles we've ever owned.
Okay, so I tried unhooking the battery and that did not work. However, I did discover that the problem only occurs when I have my heater or defrost on. At any rate, the place that changed the alternator told me that since they did the work, I could bring it back to them and they would take it to get the computer reset because they didn't want to leave me hanging. They had it for less than an hour, and called and said that it the problem is not associated with the computer needing to be reset, but is actually due to a code from the MAP sensor. He originally started out telling me there was a recall on the harness connected to that sensor and that he would call the dealership about getting it fixed for free... but alas, there was no recall. So he then said he was taking it somewhere else for a second (third if you count his) opinion. He said the check engine light (which was not on for the entire problem, just came on and threw the code yesterday) went off on the way to the second mechanic, and that there were no codes at all to be read by the time he got there. This new guy suggested cleaning the throttle body, and he said they are out driving it around now and that the problem appears to be fixed.
So my question is - is it just a coincidence that an error code appears immediately after work they did, that they admitted entailed disconnecting the harness to complete, but yet it has absolutely nothing to do with anything they may have done? Does cleaning the throttle body sound like a solution to the rough/low idle and cutting off at stops? I love this truck, I really wish it would behave!
I have a 2004 Envoy SLT, it has been great, although I have had the same problem since I bought it 4 years ago with the fuel tank, the fuel pump does not automatically shut off and it overflows. I have gotten used to it and just stop when I know I am getting close. However, my husband was spraying my car off the other night with our pressure washer with the car shut off. (I had a thousand pine needles in my hood) Needless to say, when he finished and I got up the next morning to get in it to drive it to work, the check engine light came on. He took it by one of the auto stores to have them do a check on it and they couldn't diagnose it, because they said the sensor mechanism (not sure of the name) does work now either. It is possible it just went out, but does anyone have any suggestions?
The check engine lights are very sensitive on all newer cars, and so is the fuel delivery system. It is VERY IMPORTANT to keep the injectors CLEAN. I lost track of how many miles my wife was putting on her 2003 Envoy and after about 10,000 miles without running any injector cleaner through it, the check engine light came on. That was last summer. I put 2 cans of high quality injector cleaner and a tank of premium gas through it and the light went out and has not come back on.
My best friend's check engine light recently came on on his Hyundai Accent and the car was running unevenly and using a lot of gas. A diagnostic showed "several misfiring cylinders". I asked when he had last run injector cleaner through it and he replied "NEVER". I told him to buy 2 cans of cleaner and a can of 104 octane booster and put it all in the tank with about half a tank of gas. This solved his problem. The car now runs smooth, gets better mileage and the check engine light has not come back on. As I said, it is VERY IMPORTANT to keep the fuel system clean, and it is NOT necessary to have the injectors manually cleaned EVER if you put a can or two of cleaner through the system every 5000 miles or so.
Hey all fellow Envoy owners. I have a few suggestions.
There is a recall on the fuel tank reservoir and the check engine light comes on, check with your local dealer. Pray your still under warranty.
The stalling out problem could be a fuel pump issue. I just replaced mine as it was doing the same thing as yours was after getting your alternator fixed. Coincidence??? Probably.
I have 350,000 KMS (Canada) on my XL and feel I will get at least that again. I take good care of her and she runs like a top. Maintenance is key it seems.
Maintenance and problem-prevention are the key to keeping a car a very long time. Small issues can easily lead to very big issues. Just ask my best friend who shelled out over $7000 replacing the engine in his Japanese sports car because he stupidly ran it until it got so hot the engine seized. The problem? A 50-cent piece of overflow tank tubing that can be replaced by a totally clueless woman in 30 seconds.
My wife is crazy about her 2003 Envoy. We maintain it meticulously. After 6 years we have yet to have one single problem. She wants to keep it until it is an antique.
Just to let you know:
I have had some problems with my Envoy, but the dealer has been very good with these issues.
Encoder motor: replaced no charge by dealer
Fuel tank: replaced no charge by dealer. this was a tech bulletin 07076
Wheel bearing: replaced under warranty.
The only one that was painful was the compressor for the air ride suspension
All and all I have been satisfied with this vehicle. Decent compared to other vehicles I have owed on a maintenance perspective.
After having many tighten fuel cap messages and the service engine light coming on, it was discovered that my gas tank is cracked on my 2004 GMC Envoy. This being a costly repair I did some investigating and found this to be an ongoing occurrence. I did speak to a very nice GM rep who told me there is no recall for this problem, but a special coverage. My vehicle meets all the qualifications for the coverage but I do not live in a state that this is being offered. So the expense is mine. I just find it odd that something that significant can only apply to certain states.