fuel pressure code P2540?

Here us a video if that helps

Yep, 9 times out of 10 it will be the sensor which is located at the tank on top of the low pressure fuel pump. Other possibilities are the fuel check valve is stuck open, the low pressure fuel pump is bad, or you have water in the tank (rare). Here is the location of the low pressure sensor so you can swap it out and then clear the codes. Luckily there is a trap door for the fuel pump. Check out the images (below). Please let us know what happens.

do you know the part number if it's not too much trouble plz

Sure here is the part number for the low pressure fuel pump pressure sensor.

Bosch (1561530028) Fuel Pressure Sensor

Clear the code once completed, Ken

Seems like this one maybe at the engine side. I thought we were talking about the one on too of fuel tank? Cause this one has bolts and in some sites says on fuel rail

Hmm, good call that one does not look right. Let try this one instead.

OEM Mercedes part 1635422818

Let me know, Ken

Changed it, which was under the rear seats. Got a code p0193 without check engine being on

NICE!! so we got the one problem fixed. Please start a new thread for the p0193 code. Which will involve the high pressure pump. Are you sure this car has the correct fuel, and the fuel is not contaminated?

Changed the fuel rail sensor because i kept getting p02540. As soon as i delete it and restarts it comes right back. Strange. So this sensor and the one on the left side of the rear seat which is the sender unit that also has a sensor, i replaced both with Bosch quality, i hear the right side pump strong every time i tirn the ignition on so not sure what else is there.

What do I do if I don't know if the correct fuel is in it? it has 1/2 tank, should I add a Techron cleaner?

Yep, that can help, especially if the car has been sitting.

any specific brand you tried and can recommend?

This is what I would use

https://amzn.to/4raz0ym

Let me know what happens.