I have a 1996 k3500 7.4 vortec. I recently purchased it it has been sitting for a little while but ran a drove good. I moved it one day to work on it and it died like you cut the key off. I had a guy look at it and we figured the computer was bad because I had no power to my fuel pump past the relay, the engine is not firing and my ob2 won’t connect it has power just saying no connection. I put a computer a fuel pump,fuel pump relay,ignition module,crank shaft sensor,checked grounds and wiring best I could and checked every fuse I’m lost I’m no mechanic but I’m fairly mechanical savvy any help would be much appreciated

 

Assuming you have a good battery, you say the OBD II scan tool says "no connection"?

 

I got it back running

 

Please tell us what fixed your problem! May help someone else down the road.

 

Great deal, man!