پایین بودن سطح سوخت از آستانه بخاری

A fuel-fired auxiliary heater refusing to run because the tank is below the level it is permitted to draw from. It is a designed inhibit rather than a fault — the heater shares the vehicle's fuel tank, and it is locked out above a reserve so that running the cabin heater cannot strand the vehicle.

The behaviour reads exactly like a broken heater. The heater does not start, a fault is stored, and nothing about the tank suggests a connection — particularly since the threshold sits well above empty and the gauge still shows usable fuel. A heater that will not run on a quarter tank and works perfectly on a full one is this inhibit, not an intermittent fault.

Check the fuel level before any heater diagnosis, since it costs nothing and explains the complaint outright. A level sensor reading low on a full tank produces the same lockout, which is the other half of the check: confirm the reported level matches the actual one before concluding either the heater or the tank is at fault.