I am about over this truck just had the ficm replaced and now it has shut off 3 different times and comes right back on only shuts off for about 1 or 2 seconds and comes right back on.

 

The engine cuts completely and refires on it's own, or are you turning the key?

Does it do it when driving under any certain conditions, like over a bumpy road, or just out of the blue?

 

had a similiar problem with my truck awhile back. But the speedometer and odometer were messed up. Found that the connections ( cliped together wire harness) at the fuse box came loose. Truck had the oil/egr coolers and head gaskets replaced whenit had 35k miles on it. So i think the mechanic didnt fully press the connections together after the cab was back on.
Check those connections. After fixing mine I have had no problems with truck speedo and odo and no more bucking or shutting off.

 

ok it is just out of the blue and it turns itself back on

 

Definitely sounds like a loose wire connection somewhere. Open the hood and go over all of the connections with a fine tooth comb. Be extra careful to look for any chaffed or exposed wires, if you find any, just replace that harness, these trucks (all diesels really) are super finicky with the wire harnesses. Add the heat and vibration of a diesel motor.... and it's easy to see why they chaffe in the first place.

 

I had an issue like this way back,, Mine was all my fault, When I unplugged the egr valve I didn't tie the wires back good, and eventually the wire and connecter fell down between the pullys and block, it was shorting out the sensor circuit intermitantly, drove me crazy for a week, until I traced every single wire and found the wires behind the pulley, sometimes it is just something stupid, check all your connections first.