Fuel Indicator Light

Hi all,

I'm trying to understand if the fuel sensor of my 2009 TE510 is working or not.

Before to proceed with any disassembly I would like to do some test draining the tank and watching what happens, but I don't know if the instrument fuel led work also with the motor off.
(I have this doubt because light, turn indicators, stops and horn works only with running engine).

Could somebody clarify this point for me?
Thanks

But you can test that, would the light work when engine off power on, also you can test it. Pour in the empty fuel tank like 0.5L fuel, turn key to see if that low fuel light is on, if not you start the engine then to see, if not working take fuel pump assembly out and look is the orange wire ok