I'm having a lot of problems with a 2003 Envoy XL SLT that my friend bought from my Mother In law. It has 114,000 miles on it. The A/C stops cooling when you change any of the settings, other than outside vent, at 60 degrees on the thermostat. It cools fine if you like to freeze or wear a jacket in 100 degree weather outside, while you're in the SUV.
Then today, was just driving along, and the check engine light came on for no reason at all. It still drove the same for 300+ miles. I'm not a mechanic, but with all the problems that I have been reading, it sounds like the computer on these SUVs does not work properly. That's just an opinion for now, but I'm going to have one of my friends check it out.
The computers on these vehicles did have problems. It is very important to find a dealership that has good, computer-certified service techs. When we bought our 2003 Envoy, I was aware of the touchy computer issue, and sought out a very good dealership with highly qualified service techs, who made sure the computer was properly set before we ever drove the car off the lot. As a result, we are now at well over 100,000 miles, and have never had one single problem with this car. It has not even required a brake job yet.
As for the "check engine" light, these generally mean nothing. Ours has been on since 2006 in one of our cars and since 2010 in another. Both cars run flawlessly, and show zero problems. There has been no drop in performance or gas mileage. One codes as "EVAP system", which means nothing, and one codes as "running too cool", which is actually better for the car anyway, so I don't intend to fix it.
Some localities have been in cahoots with car service facilities to fail cars in inspections if a check engine light was on, in order to generate profits for shops and dealers. In a move toward fairness, the large city near us recently did away with this practice, because of the deluge of complaints they were getting from outraged car owners, who were being charged thousands of dollars by unscrupulous shops to turn off the lights.
I am having the same problem with my 2003 Envoy SLT; did you ever figure out what the problem was?
Hi, we had the very same problem with our 2004 Cadillac SRX. After some research, I removed the security fuse from the fuse box and the problem went away. Somehow the car thought it was being stolen and locked itself up. When I took out that fuse, I could actually feel the car relax. Maybe this will help you.