A 98 coach may not have had the extra braking wiring. The wires if you have them would be coiled up to left of steering wheel under dash. Will have to use flashlight to find.
An easier way maybe open your trailer plug and see if ever wired or you may find the wiring coiled up near the jack.
Heres a
link for trailer wiring and Newmar has always wired standard, unless previous owner did his own wiring job.