I have an 04-4 door Blazer. "Gate Open" light was suddenly lit up. I opened and closed the back window, ever since I cannot open the window or back door using the remote or any other method. It does make the normal unlocking sound when using the remote and door panel switches. Any suggestions on how to get this apart without going to a mechanic? (I have disconnected the battery already)

 

You can manually open it from inside. You'd need to pull the plastic panel and there's a metal lever to release the glass. There should also be a rod spanning the width of the gate that controls the latches along the edges.

I have the dropdown tailgate like a pickup rather than the gate that lifts up but I've manually released the door and glass on both types of gates before. However, I can't remember if the plastic panel can be removed from the liftgate while its closed.

Here is a picture of mine that shows the location of the glass release (blue circle)and the latch release (green arrows).