Detroit 60 shut down doesnt start

My ddec 4 did this also. Started it one morning ran for about 20 minutes and died and wouldn't start back up. Like others have said check fuse coming out of the battery box, starter relay, acc relay. Mine ended up being a fried ecm. The test ecm will let you know.

 

I also have a 1999 Pete with a Series60 & experienced this EXACT SAME problem a few years back. I had intermittent no starting issues a few times, plus my truck would just shut off running down the road with NO warning. Check both wiring harnesses at the cab firewall (they are on the upper drivers side of the firewall). 1 runs to the engine & ECM, the other runs under the cab. I had a wire on the cab harness that got frayed & cut underneath going over the frame. Peterbilt factory routed it in a bad location & didn't think to use a few $$ of extra shielding to prevent this from happening. Of course, this was AFTER we had replace the main cab harness & the engine/ECM harness. I had other wiring issues as well, which got fixed up when replacing those other harnesses too. Also check the 2 15 amp fuses that run the engine/ECM. Mine are next to the oil pan. The main cab harness, as I recall, was $3400. The engine/ECM harness was $1300ish ( I recently picked up this harness as NOS & brand new still in the plastic from a dealer for $600) & the cab harness was like &1800ish. Good luck!!