Good afternoon,
So I have a 2000 GMC Jimmy and its been raining hard here in Michigan, then getting cold right after. Ever since this has started the Gate Ajar light will pop up on the dash and sometimes, the back glass wont close unless the doors are locked. I don't know what is causing this and i had to press the button on the dash that cuts the interior lights off to prevent battery drainage. I have tried opening and closing the glass hatch to see if the light would go off but still no hope. This is very inconvenient and I would really appreciate it if someone could help. Thanks.

 

May just be a faulty latch. I would start with seeing if you can pull one out of a Blazer or Jimmy in a salvage yard, might get it for fairly cheap, and I don't think it's a common failure (I've never really heard of any issues with them at least) so installing a used one shouldn't bee too much of a long term issue. I do not believe there's any adjustment in the latch as far as holding it in tighter or looser, it's most likely just a replace it situation...

Is yours the whole rear hatch type or is it the lift glass and the drop tail gate style rear end?

 

It's the full lift gate with the flip up window type.
I do believe that it may be a common failure on these because i did a google search and it came up that a lot of people get this issue but i have not found a solution:/. I have noticed that the light would come on in the morning when its cold, but after the truck gets warm it goes away, but this is a extreme inconvenience. Whenever it happens I can not use my rear wiper (which has its own issues lol)