We have a 2002 GMC Sonoma Extended cab that we bought used in 2008 to tow our boat. It does a great job towing, but the damn thing has had a ton of things go wrong with it. The most annoying one is a recurring issue with the 4-wheel drive. It has a push-button selector in the cab and it will not shift into 4HI. It doesn't even "try". You can get it into 4LO if you put in it neutral and then shift to park while the lights are blinking, but 4HI just does not work.
We've had it fixed three times, twice at one mechanic and the third time at another, and all three times they said it was an issue with a vacuum line. All three times it failed to work again after a few months. We had another mechanic tell us that the motor in the transfer case will get gummed up if you don't use it enough. I don't know it that makes sense, but the truck did sit more than it was driven until I got my license last year (I'm 17). I did some research and I guess the most common problems are the solenoid freezing up that actuates the vacuum or the vacuum line having a hole burned through it by the exhaust. I would guess, based on having no response from the status lights, that the solenoid is frozen. Anyone have any better ideas or know how to fix that problem?
This is a big issue now because we got an inch of snow last night and I had absolutely no traction on my unplowed side-street this morning trying to get to school. I had to put it in 4LO and go 10MPH to get out.