Hammer, tap, twist bang and pop test...
If the engine sounds strong but simply cuts off, then you may be right, it could be an interlock.
It could also be an interconnect.
So what you need to do is sneak up on the problem.
Open all of the access doors so you can touch everything around the generator.
Make sure it is full of water if water cooled.
The sensor is usually real close to the top, when the engine is running it drops a little, and if driving causes it to be at a different attitude then it could think it is out of water.
Start it up and let it come up to operating temperature.
Now start to GENTLY tap and wiggle things.
First would be where the control cable attaches from the coach to the generator, twist and wiggle to see if anything happens.
Next repeat for every wire you can see.
Lastly, get a short stick like a broomhandle and start tapping things.
The oil sending unit, the temperature sending unit, control unit etc.
If none of this works, then you may need to see if you can remove the control line and manually run the generator as if it was not in the coach and take it for a drive.
The short of all of this is you are going to need to chase down the problem, hopefully you can simulate the problem while parked.
Tony & Lori
1989 Country Coach Savannah SE