Mercedes fuel gauge

Question edited for a lot more clarity, and add maker.
Question moved to maker category.

These are all function of the Body Control Module. You need an auto electrician with a pro grade scan tool computer and access to factory technical bulletins.

https://www.google.com/search?q=mobile+auto+electrician+near+me

No clues in here.

Mercedes-Benz Vito / Viano (W639; 2004-2010) fuses

Fuse Box Diagrams https://fuse-box.info > mercedes-benz > mercedes-ben...
The fuse box is located in the engine compartment on the passenger's side. The location of the fuses in the engine compartment: Mercedes-Benz Vito / Viano.

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It is usually malfunction fuel level sender units in the tank

there maybe a switch between the two tanks ,it must be replaced by a new one,to let the fuel on the other tank pass into the fuel pump.

See the dealer.
GL,
TD

probably a stuck float in the tank

The gauge circuit runs through the pump fuse. Most likely the sending unit has failed inside the tank. :-(

Fuel level sensor is in the gas tank, may be faulty or just dirty, make sure to fill the tank entirely full with premium unleaded, ad a high quality fuel system cleaner / de-gunker, this may clean the sensor enough to feed back to the gauge. It could also be the fuel gauge itself, but that is less likely. Mercedes will be happier with at least 1/4 tank of fuel at all times, and don't skimp on low octane gas!
As for the check engine light, you may have a bad gas cap... believe it or not a gas cap that doesn't seal properly will throw the check engine light. If you get the codes read (for free) at an Autozone or similar parts store it will likely read "evap system" as the problem, which will likely end up being the gas cap.
Take your car to a service center that does a true "flush and fill" of your a/c system. Those little canisters will just waste your money, and they never truly clean and re-lubricate the system like a flush and fill will do.

psi diff inside tank is wrong.
use a OEM fuel cap to make light go off.
make sure it clicks at least 3 times.

Follow normal troubleshooting procedures.
Do It Yourself Diagnosis and Repair

You can try to clean the ground behind the instrument cluster to see if that helps but most likely the sending unit has gone bad in the gas tank.

you need to replace the fule gauge sending unit inside the fuel tank, as far as the waring messages go u need to have the system tested for a fault code that is stored when these lights come on, the requires a trip to the MB dealer.