Brakes

Fround the problem it is a air leak in the line

The alarm means your primary air system pressure has dropped below a set-point, likely 60 PSI, due to your leak.  If it is a hose/line you can "cap-off" upstream of the leak it might be enough of a band-aid to get you to a place where you can fix it properly.  I wouldn't recommend doing it if the hose in question leads to a brake, but if it is going to say an air-spring, you can stop the leak so your coach can get up to proper pressure and limp along slowly to the nearest truck shop, etc.  I carry an assortment of 3/8", 1/2", and 5/8" DOT caps and plugs (NPT and quick connect) just for this reason.  Good luck and stay safe!