A green 120 vac LED pilot lamp connected between hot and earth ground is a good way to tell if chassis ground exists inside the rig. I learned the hard way to connect a RED 120 vac pilot LED between chassis and earth ground. Muse the possible combinations of yes/no red and or green lamps.
I learned this the hard way. A worker at an RV park worked at the park's general panel when I was north in Barra de Navidad. When I returned I grabbed the door latch. Spent the remainder in bed with a badly irregular heartbeat. I have one set of lights stacked near the main entry door, the second beside the stove in the galley. No power draw. Reliable. My ground rod "fix" blew the hell out of the Boca de Iguana's RV electrical system. I related this story some months ago, here. "Blowing the hell out of" is defined as smoke boiling out of concrete ground hatches, fire and a melted distribution panel near the office. They could not find a breaker so they wired around it. NEUTRAL IS NOT FUSED OR BREAKERED. A neutral to ground short is wide open as much as the wiring will tolerate.
US campgrounds are different. If I die down here, the management would fix the problem after paying the cops and they would all shake their head sadly and say "Heart. Obviously. What a shame"
After I pound in the ground stake and the campground grid goes up in a mushroom cloud it's pure Tough S---