I have a 2011 GMC Acadia Denali. When I turn the key it doesn't even click, but I still have headlights and interior lights, my gauges work, I can roll my windows down and move my seat (both are electric) nothing dims. I tried to jump start it but it wouldn't even take a jump (didn't change anything when tried to jump start it). I have also replaced the battery thus did not help. I have checked the fuses and relays for the ignition and starter and they are all fine as well. What could be the issue? So far I have been told possibly the starter or maybe the computer and I have also been told that it sounds like it's going into "limp mode" or possibly a ground wire issue. My check engine light is on but these are the only codes I am getting P0455, P0496, U2142, U2100, C0710. My message center also has the following messages on it...traction control is off, service stabilink, service traction control system, also tells me that I have a tire that needs air (but tire is fine) and will randomly tell me tighten gas cap as well. Please help! I can't afford to have an expensive yard ornament! Thanking you all in advance.
Your neutral safety switch may be stuck, intermittent, out of adjustment or disconnected due to running over a tree branch or other debris.
Put your foot on the brake, turn on the ignition and move the shift lever briskly from Park all the way to Low and back to Park several times. Leave it in Park.
See if it starts.
If it does not, repeat the process but end with the transmission in Neutral. See if it starts.
If it does not start, return to Park. As HandyHowie suggests, the next step will be to measure voltage at the starter relay while you attempt to start it. This normally takes two people and a voltmeter. The results of that test will determine the next steps in diagnosis.