If I depress the service brakes, parking brake engaged, and put the bus in either D or R, a "buzzer" in the dashboard sounds... on/off, not constant........ If I depress the service brakes, release p...
As suggested by Wolfe10, if your chassis if Freightliner, call the Freightliner help desk (free service). Have your vin number handy so that they can find your chassis records.
I had that problem, and the sensor was located along the frame rail, driver side, just in front of the rear axle.