Gravely ZT 2348 PTO problem

Gravely ZT 2348 PTO was was fine last week when I parked it. This week however the PTO would not engage. I hot wired the PTO and it engages just fine. Bought and installed a new PTO switch and relay and still no working PTO. Safety switches all work. I suspect a wire short but after trying to trace down the PTO circuit I gave up. Lots of wires on a new mower these days. Dealerships says new wire harness is 150 dollars. Should I get new wire harness or can someone tell me how to find the bad wiring? Also I noticed the parts diagram shows a diode where the harness and PTO wire hookup. what does this diode do and could it be my problem>

Can I just hot wire the PTO/clutch and run it that way till I resolve problem?