I am basing the following off of memory, so it could be way wrong.
From what I remember reading is that the CO/Propane sensor sends 12 volt DC power to the propane solenoid. The solenoid then opens up (it's normally closed) which allows propane to flow to your appliances. If you don't have 12 volt power for any reason via the sensor, then the solenoid closes and thus shuts off propane.
The sensor, when it goes into alarm stage, just shuts off power to the propane solenoid (and it closes), thus shutting off the propane.
Now here is the part that you may need to verify, and may make just bypassing the sensor a little tricky. From what I recall is that the sensor provides 12 volt DC power to the solenoid, which then in turns opens and allows propane flow. I think then the sensor steps down to 9 volt DC to keep the solenoid open.
Bypassing the sensor with a full and constant 12 volt DC direct (without the 9 volt stepdown), might could overheat the solenoid or something, but here again this is not gospel coming from me.
You could just temporarily do away with the solenoid at the propane tanks, if you could easily replumb the propane fittings there. This might be the easiest route, then hook the solenoid back up when you get your new CO/propane sensor in.
RV's like mine, although they have a propane alarm/CO sensor, do not have the added propane solenoid shut off valve like your motorhome does.
Either temporary way you go, you seem to be without the required sensor that could save your life. I would advise at least getting a battery operated CO sensor at a hardware store (like a smoke detector) and using it in the interim if you are going to be operating propane appliances.