07 LT 5.3L Sudden no start/crank

tc8510 said:

Have you checked all your grounding wires? I had this same issue. It came down to my grounding wire that goes from the firewall to the top of the engine block. It was hanging on by a thread down by the block.

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J-Herkel said:

Alright so after some more diagnosis this evening, I had my buddy hook up his $7000 scanner and scanned the entire vehicle. The Theft Module is good. The BCM was good. The ignition switch is reading key postion correctly, the signal is being sent when the key is turned to the crank position. The ECM was good but detected a fault in the Start Relay Circuit (P0615). So we used a schematic and traced the wires to the connectors below the Fuse box that the Fuse box itself plugs into. We tested the relay terminals. 30 is good (12v). 87 is good (12v). 86 is good. 85 (ground) is not good. No reading. We took the fuse box off and out and tested the terminals on the plugs below. The power (+) side to the relay is all reading. The ground (-) is also reading fine. Next I pulled apart the fuse box and we tested the contacts on each side of the board. The power side has continuity. The ground terminals do not. We touched the relay ground terminal to every terminal in that bank that it leads to and no continuity. As weird as it sounds, it seems like the fuse box relay circuit went bad on the fuse box circuit board. I'm assuming I can put it all back together, use a thin wire and stick it in the ground side of the relay, ground it to the frame, insert the relay and see if it cranks. Thoughts? Ideas? I'm not an auto mechanic but I'm doing my best here.. I did see a little bubble on the board. Maybe it has nothing to do with it. Idk. I'll attach a picture.

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