Pioneer DEH-P8400MP Power Problems

Hi guys, new to the forum but maybe you guys could give me some help. Last night i went to dinner and the thing was working fine. I get out of the restaraunt and start my car. The head unit does not come on. I hit the power button several times and nothing. I get home, go get some wrenches and disconnect the battery hoping that might do something. Nada. Check the fuses they are a-ok. I have a 1988 mercedes benz 190 if that matters. If someone could shed some insight into what might be happening, and a way to fix it that would be most excellent.

Unfortunately there a few different things that could go wrong with a deck that would cause it not to power on.  Your deck uses (2) fuses, one for the switched power and one for the constant.  Even though the one labled "Radio" or whatever might not be blown, the still might be another.  Check your cigarette lighter and all the other accesories and make sure that they still work.  Also there are fuses on the back of the deck that could have blown.  Another culprit is lose wires and sometimes the decks just die.  Without really looking at it, it is impossible to tell.  You might just want to take it to your local car audio shop and have a professional look at it.

you might want to check the fuse behind the radio also.  Do it right the first time

i checked the car fuses for the radio as well as the one that is inline from the wiring harness. They are all ok. Im gonna check to see if the line is hot tomorrow, but if it is then i guess somethign got messed in the headunit itself

i got the same deck, i ran into radio shack came back and it would turn on, id unplug it plug it in and it would come on for a sec of the faceplate would move then it would go off. Luckily i had a service plan at bby so i sent it out and it turns out the cable from the face to the deck had to be replaced, got it back within a week and its all good.

I have the same deck had the same problem twice. Its usually the connection on the back of the faceplate. If the plate is worn we it connects to the face then theres your problem