Let's see how good you guys are I have a 99 ford expedition Eddie Bauer... fried 3 pcm's
 

:'(Me and my 13 year ford master tech can't figure it out it has a 5.4l and every time we put a new pcm in it and program it to the pats with no problem we try to crank it up and it fryes the pcm every time (3 times now) when it is attempted to crank.... please please help me I don't even know where to start I've looked at all of the wires that I can see and no chafing or bare wires... I naturally think that the pcm is short to ground because it takes out the main or the largest processor in the pcm but have no clue what would cause this? Please help me I have a week to get this running or I can't finish college because my wife needs a car to take my children to school and I've already burned up 900 bucks in pcm's I can't do this again...

BTW when it frys the pcm the fuel pump runs nonstop with the key on...

While there is a hundred different wiring problems that can cause PCM issues, I would think frying a PCM has something to do with mis-directed main power. I would take volt reading between the battery negative and the body, then again from the battery negative to the engine block, and finally from the body to the engine block. At no time should the reading go over 1/2 a volt. Try this with the fried PCM connected and with the key on, then again while holding the key in the start position.

Thank you for the response I will check that tomorrow after work... if the voltage so over that what should I do from there?

But just out of ignorant question do you think a lack of ground would fry the pcm over and over?

Then you have a bad ground bonding jumper which in turn redirects current to where it shouldn't go.

Yes, it could fry the PCM or any other voltage sensitive device on board.

Please give me idea of how to do all suggestions....

Alloro just out of curiosity what is a ground bonding jumper?

Okay, THIS IS A DUPLICATE THREAD.... POST IN THE OTHER ONE.

LET THIS ONE DIE.....

Or...we could let the other one die and continue in this one. :-X18

So I have checked all grounds and batt + to pcm and everything was good... but when I had my wife turn on the headlights they didn't come on, when I had her flip the switch to give it a load the pcm started to smoke like crazy... can't find any shorts but keep frying pcm... oh and the highbeams came on until the smoke started... PLEASE HELP ME!