Well, Long and short of it was that I gave up in 2015. I read an article that the DOJ sued GM $1B for covering up the engine shutdown which resulted in 17 deaths. I called GM corporate and they send me back to the local dealership. Although most of the problem in DOJ case was attributed to the faulty ignition switch and I had changed the switch too with no avail, GM worked with me to pick up another vehicle. I ended up getting a Cadillac SRX with a whole bunch of incentives and dealer took the Hummer. I am happy with the SRX but never found out the cause of the shut downs after spending thousands and thousands of dollars.