I have a 2003 yukon XL. Never had a problem in 2 years until now. Went to start it the other day and it was dead. No interior lights, radio, etc. Jumped it with my other vehicle and it started fine. Went to turn it off, removed the key and engine was still running. Fortunately, the dealer was still open and I drove it over to them. They were all very perplexed. The tech indicated he never saw anything like this before and would need to consult GM today to figure out the problem
Any thoughts on what could be going on? The tech did remove the ignition cylinder and the ignition module and it still continued to run.
Also, if this happens to me when the dealer isn't open, how do I stall the engine?