Hello, I have a 2011 GMC Acadia. I have had it now for three years I got it used. Since the day we bought it, the check engine light would come on every so often, and go out with no issue. Once in a while, it would read high voltage followed by the engine still running when the key is off.
So, we learned was because of under-voltage in the battery. Then, when the battery would lose more volts the key would get locked in the ignition and couldn't be removed. The check engine light would be on regardless if the key was off. The check engine system light would next drain the battery down lower. Now, the car appears to be dead. So, I could make all this go away by disconnecting the neg on the battery and recharge it to full. SO, the question remained "why does this happen?"
Well after doing some digging I found the Acadia had a string of leaky drains from sunroofs, but I don't have one, never less, I pressed on. I saw someone on youtube, say to check behind the front passenger side carpet, just pull it back from the wall and see if it is wet.
This turned out to be the case. Water was getting through the hood cowl, it's only tac welded inside there. Water is getting through the tac weld and dripping on the electrical fuse box behind the glovebox. When it gets wet the system goes crazy with charging system error codes.
I tried my best to seal it up to my self but it still did not work. I instead covered the fuse box with something preventing water from getting on it. Since then we have had many rainstorms, and not once has the check engine light returned.
\GMC please look into this mess, I have spent so much time and money, while mechanics go down the wrong rabbit hole. People, If you are having similar issues please check to see if this happens during or after it rains.
