I've got a 2007 Chevy express 2500 4.8L 2x4 with a no start condition. This is what ive done so far. Checked battery voltage(12.7v). Checked ignition switch at switch and to the crank fuse under hood. get 12.7v to crank fuse when key is in crank position.Checked starter. pushed 12 volts to starter signal wire and vehicle starts. Tested wires going from the starter relay to the starter. everything checked OK. getting voltage to the relay but no getting ground signal to trigger relay. I'm confused on where to go next. If i could get so help i would really appreciate it. Thanks

 

Update: Ok I figured i would give a few thing a try. I have a spare truck that i can pull some parts from so i went ahead and replaced the fuse box and had no change. If anyone could help me with so wiring diagrams i would really appreciate it. I've followed the wiring harness and checked all the ground wires coming from the main wiring harness.

 

Update: Well couldn't find any wires that were damaged or connector unplugged so i took a fused jumper wire and ran it to the crank replay and the vehicle starts and runs but really rough. pulled codes and getting a P0200 and P0300. injector circuit malfunction and misfire. i think that i am loosing a ground some where in the system causing all my problems. going to call Chevy and see if they have any ideas now.