There should be a safety interlock (or several) in the system. There are probably many throughout your bus.
You need to determine if the switches on the lift and lift door provide (or break) a ground (most likely), or a powered circuit (less likely) to tell the system the door is open or the lift not stowed.
If they provide a ground then you simply attach that wire to a ground and you're good.
If they break a ground then removing the wire is all you need do.
Most likely the system is designed so that the stowed position provides a ground and the open door or deployed lift opens the ground and that signal tells the interlock system to prevent gear shifting, engine starting, sound an alarm, or whatever the spec was.
This provides that if the circuit is damaged and the ground is broken it will activate the interlock. If designed so that the stowed position breaks a ground then a damaged circuit could be interpreted as a stowed and safe condition thus defeating the purpose of the interlock.
I used to work on E350 transit buses with lifts and I've designed and installed replacement interlock systems when the fancy (and expensive) circuit boards failed.
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We've done so much, for so long, with so little, we now do the impossible, overnight, with nothing. US Marines -- 6531, 3521. . . .Ret ASE brakes & elect. Ret (auto and aviation mech). Extra Class HAM, NAUI/PADI OpenWater diver