I've searched high and low for this, found a few similar scenarios but couldn't find the fix. I have a 2008 lmm. It has been driving fine. Yesterday drove to work. later on drove to lunch. Then when I went to go leave work, it tried to turnover and didnt. From then on out, all I get is one click when I turn the key. Everything works as normal, dash lights, radio, headlights, etc. I tried jumping the starter, it sparked and made a clicking sound but wouldnt budge on cranking. I briefly checked the connections at work, and even had someone try and jump me off and no luck. Battery gauge on dash and my cts insight are good. My cts read 12.4 to be exact. I read that maybe it needs the ECM reflashed and it was a common problem? I havent checked with the dealer yet to see if the previous owner has had this done or not. The people that needed this done said they didnt get a click or nothing though. So I'm lost? I had to drive my girlfreinds car to work today, so my truck is still sitting in the parking lot. I'm hoping it is something simple, I don't really have the time or money to have it towed and everything else. I will say occasionally over the past month it would start a little slower than normal but wouldnt do it everytime. Could it be the batteries? Any help would be much appreciated!