location of j*** datalink cable? from where to where?

im having issues with the dash acting up, and the DID digital display not working. It lights up, but no actual readable display. I'm reading online at other sites that the J1939? Datalink cable may have chaffing issues/ rubbed wires etc. that may cause my issue.... thing is -- where do I look for that cable or wires at? where does it enter the cab at? and where does it go? (firewall? under the dash (doghouse) area? is there an available online manual that would show the Chassis/ electrical wiring locations? the local shops are of no help they want to troublehsoot the truck and go "fishing" for the problem at $125 an hr. which I refuse to pay right now.

2nd issue-- ABS light on dash is on- yet when testing the ABS system (cycling the brakes with key on- engine not started) they work fine??? is this a sensor issue? -- I would use the dash digital display to try to attempt to figure that out- but it don't work right now either =o(

truck is 2000 VNL770 n-14 1st gen autoshift.

any help and info/ pics are greatly appreciated...THANKS!!!