Would a bad pcm or pcm relay cause everything in the truck to work properly when running, but when you turn off the truck, and everything goes off like it should, about 15 seconds later, it all comes back on? Without the key in the ignitiion? The fuel gauge stays on, the rest goes off and comes back on, windows, door dinger, radio, dash controls, (those actually surge to the highest point before coming back) all the while draining the battery rapidly? Like, if we start the truck back up and turn it off 2 or 3 times, the batteries are gone. New batteries. With the pcm relay in, the battery light is on, when we take it out, the battery light goes out and the rest of the lights get brighter. That is why I figured the problem was that relay, but we changed it out. So far we have changed out:
The ignition switch
checked all fuses
swapped relays around
swapped instrument cluster
tried my sons f350 pcm in place of mine, no change (different programming?)
checked all grounds
I see others with problems of things going off, but no one mentions coming back on. Anybody?

 

I would love to know what you came up with! I have the same problem...
I'm also trying to figure out the difference in a manual vs. Automatic PCM? Have to do with the tranny or gauges???
Thanks,
D

 

The difference between the manual and automatic PCM is the software in the automatic PCM controls the transmission. That software is disabled in the manual PCM.