Typically the coach 12v system uses a white wire as ground... at least mine is. Usually, but not ALWAYS, a green wire is ground in an AC circuit.
Does the wire go through the floor in a plastic wire loom? Looks like it's just looped around frame members... maybe someone was using it as a temporary zip tie?? Where are the ends?
On closer inspection, it does look like it goes up through the floor... go in the coach and find where it emerges from underneath.
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