Maybe someone who has access to their motorhome can check this out for me.........ours is 2 hours away at the dealer for repairs.
If I recall correctly, even WITHOUT the key in the ignition, if you press down on the brake pedal, you should hear an electronic/hydraulic sound along with an increase in resistance pressure felt on the brake pedal.
As I said, I can't verify this with my own unit, but maybe someone out there can?
If there is any kind of electrical circuit with a fuse, you may even hear it without the keys in. Don't know if this will help or not.