Hi, Guys. Thanks a lot for all the great info. I just purchased a used 2005 Tahoe a week ago. The "Service 4WD" message appeared yesterday. No other messages appeared. I selected 4WD, and it went in OK. Just wouldn't come out! I drove around the yard a little bit, reversing direction and gear, and eventually it went back to 2WD. Subsequent attempts to re-engage 4WD failed. The 4WD (HI) button would flash for 15 seconds or so, then extinguish. Upon selecting 4WD, I heard noises down below as it attempted to satisfy the request. Now, when I select 4WD, either HI or Low, the indicator lights stay black and there's no activity. It's as though the computer had locked out the switch panel 4WD functions.
The Tahoe has 93,000 miles on it. It was a fleet owned vehicle. I'm not sure if that's a good thing or a bad thing. I assume it didn't go off road. The undercarriage is cleaner, corrosion-wise, than any of the Tahoes we looked at.
Monday, I'm going to take it in to get the Drive Train Diagnostic Codes read, and have them put it up on the lift and check out the transfer case fluid, then change it, and see what happens.
The used car dealer I bought it from is down in New Jersey, about an hour and forty-five minutes drive each way! He said I have to bring it in for servicing. By the time I do that, I'll be approaching the limits on my one-month, 1,000 mile warranty. Hmmm.
Plus, it's a real drag driving down there, we'd have to take a chase car along, leave the Tahoe there, come home, drive back down, etc., etc. etc. What to do?