Code P0451, Fuel tank pressure sensor?

Yep, the fuel tank pressure sensor is "Trunk, center front"

P0451 trouble code indicates a problem with the evaporative emission control system pressure sensor range/performance.

Check out the images (below). Let us know if you need anything else.

Thanks for the reply! I did find the sensor and it looks like it's a one piece. Do I need to replace the whole piece and if so? What tool do I use to remove the old piece? Thanks

You will need to contact the dealer to see how the part is serviced, which I would think it is all one piece. I don't think you will need special tools, but it does not show us how the part is removed, can you please upload images of the part so I can get a closer look to help walk you through the job?

I was able to pull it out and inspected for any damage and showed no signs of defects. So, My last question is that the gas gauge in the dashboard shows accurate What else could be the problem why the code PO451 comes on after I replace the gas cap and the gas gauge still works perfectly fine?

P0451 trouble code indicates a problem with the evaporative emission control system pressure sensor range/performance. This could be the gas cap, maybe you got a defective unit, also does the new gas cap have an O ring seal on it?

Here is the pic. I did more research about this piece and it's called fuel tank sender unit. Is this sender unit part of the fuel tank pressure sensor as well or is the fuel tank pressure sensor located somewhere in the car?

Yes, the sender is part of the pressure sensor. It looks strange with those fasteners, I will forward this post to see if anyone has seen these before.

Any Evap leak, either under vacuum or when under positive pressure such as vapor generation like Ford uses, can cause a skewed fuel tank pressure reading. A system this old is pretty basic, I would make sure the Purge solenoid is fully closed and not leaking first, its a 2 wire solenoid that should be closed and sealed when no power is applied, and the canister is in the rear of the vehicle (5th diagram). We usually would use a smoke machine at about only 1 psi to check for Evap leaks. But you can do a visual inspection of the canister and its hoses for any cracks or loose hose clamps, The Purge valve is located in the engine compartment (4th diagram). You shouldnt be able to blow air through it with it deactivated.
The Vent valve on this vehicle is not even controlled electronically, it acts more like a PCV valve, being spring loaded, I can see that easily sticking one way or the other causing a leak. (diagrams 6,7). Just components to check that can throw off a tank pressure sensor. If this post is still active.

Thank you AL514! nice input.

If you mean the two gray parts they are the spots you put the MB puller in to release the sender. You put the puller pins in those and you push down on the sender and rotate it counterclockwise to release it. You can see the tabs on this one that you release.

Thank you STEVE W!

Thanks for the insights! By any chance, you could lead me to where the location of the Purge Solenoid?

Fyi, it matters greatly if the Mercedes scanner is being used to read the codes. If you're using a generic code reader in the obd2 port and not the OEM scanner or good aftermarket you can be chasing the wrong code.

Thanks LOU P , long time no see thanks for chiming in!