I recently came across a DMH-1500NEX that was pulled from a car that got into an accident. They said the unit wouldn't power up, but I wanted to roll the dice to see what was wrong. It came with a idatalink RR, which I needed anyways. 

Long story short the first thing I did was pull the fuse and to my excitement it was blown. I replaced it and powered up the unit, no logo but it showed a black screen with backlight for about 5 seconds then the reverse camera was triggered. I can tap the screen to show the lines, but none of the buttons work or make any beeping sounds. I have put 12v and ground to the reverse sense wire and still no change. I don't even see the pioneer boot logo or anything. 

I attempted to reset the unit by pressing the little pin hole on the right side of the head unit, same behavior. I've booted and held every single button for 15-30 seconds thinking it would bypass and maybe let me either disable to change the setting.

I am at a complete loss on what else to do. I have disassembled the entire head unit down the board to examine for any burns/shorts (since the fuse was blown). I didn't find anything. Do I have a brick? Is there anything I can do?

p.s. One interesting thing I did try was to plug in a android phone to the back and android auto did boot, and showed the restriction prompt saying that I needed to put the car drive. Most likely this was due to the head unit thinking it was reversing. 

Just a quick update on this as well. Perhaps it really is bricked... I tried to plug in a video input from a dashcam to see if it is in fact some how triggering the reverse cam by default but no video is playing on the head unit when it is in this state. Which leads me to believe perhaps there is some other issues underneath it all. Again gladly hear any thoughts or suggestions. Thanks again.