I added an exhaust brake to my 94 HR Endevor and wanted total control independent of the 3060 ECU but your brake relay or what ever they come with is probably in a plastic box 8-10 inches square on the inside firewall behind brake pedal, maybe 6-8 small bolts on the lid, remove lid and get it started, idling and if it's still loading and unloading feel the relays to see if 1 is clicking, if so you found THE relay, the hard part will be determining the source of the signal to the relay. Years back returning from a race I stopped at state line, Nevada/California and when I started to leave the engine started but the do not shift dash warning was flashing and no forward or reverse gears. I removed and opened the keypad and control ECU and I believe there is 5 separate boards, and a few electrolytic capacitors, old school nowdays, they look like little Coors light cans about the diameter of a pencil and around 1/2 in +/- tall, 2 wires. They have electrolytic fluid in them when new but with age they get sensitive to cold temps. I positioned the boards on the floor for access but still connected and 1 by one took a wooden match, lit it till burning well, blew it out and touched it to a capacitor and quickly started engine, finally after 2-3 caps the do not shift light wasn't on. Fine, know it has a bad cap but luckily once started and with heater on I drove home without incident. I repeated the high tech troubleshooting the next day to see how many caps were bad, 1 at a time, but ambient heat was high enough and the problem wouldn't repeat so I did the reverse, 1 at a time, got frost from the freezer in a baggie, touch each 1 and start engine. Sure enough the do not shift light would come on, then "match" it and it would go off. Found an electronics store that had them in the capacitance range I needed and replaced them and was good for 5-6 years. The next problem was not repairable but found a core module online and sent it to the guy in Texas, John at ???? instruments, a search will find him, $500.00 and still working no problems. It's either John or a RV junkyard but it's still a used 1 and can croak at anytime, good luck on price for a new one, was $3500.00 back then, who knows now. John will make it right as long as a board isn't burnt. Sorry, It's a term paper post, I know, but it's everything that's relevant that I can remember. 2 signs of aging, 1 is short term memory loss and I forget what the other 1 is.... GOOD LUCK, remember, humans built the dang thing and you're human and can get it going with some head scratching. Lee