Bits of info that may be correct but bare checking are the wire ID that should be stamped on the wire side as the example shows.
Does it seem the LP level sender is working correctly? That cuts out lots of the wire ID question.
We don't get the best wiring drawings for the newer units, so there is a bit of guessing in this as I tied it together using the ID chart here:
AND that makes it really open to mistakes, so if you find different, go with what you see!
What I might expect to find is the power comes off before the coach disconnect switch, so that it stays hot all the time (parasitic drain?) on 16 gauge yellow wire labeled GJ to detector, then UH to valve and UJ to switch where it likely meets ground to close the circuit.