My 2005 yukon xl will, at random, shift itself into 4 wheel lo. it happens while driving and at speeds of 30+ mph. all of the lights on the push-button 4wd control module will light up or flash. no amount of button-pushing will disengage 4 wheel drive. i the car will slam to a 5 mph crawl when it does this. also the traction control system deactivates at the same time. has happened over 40 times now.