Füllstandsensor des Alternativkraftstofftanks defekt

The sensor reporting how much gaseous fuel is in the tank has failed, or its float arm has stuck.

Level has to be measured separately from pressure, because pressure cannot tell you how much is left. LPG sits in the tank as a liquid under its own vapour pressure, and that pressure is set by temperature rather than quantity — a nearly empty tank and a nearly full one read almost the same at the same temperature.

So the tank carries a float on an arm, read magnetically through the tank wall so that nothing electrical penetrates a pressure vessel. That arrangement is why these gauges are less accurate than a petrol sender, and why the commonest fault is mechanical rather than electrical: a float arm fouling on the tank wall or on debris, pinning the reading at one value while the circuit tests perfectly.

It matters more than a petrol gauge fault, because of the 80% rule. A gas tank is deliberately never filled beyond about four-fifths, leaving vapour space for the liquid to expand into as it warms. A tank whose level is misreported can be overfilled, and an overfilled tank warming in the sun has nowhere to expand.

The usual owner experience is a gauge nobody trusts and a car that runs out of gas without warning — recoverable, since it falls back to petrol, but worth fixing rather than working around.