Ok, I see..

I was planning on taking an ohm reading on one of the cars here tomorrow
at a 2.5 reading and see what the sensors says .. That way, you could sub. a resistor of that value to see if the gauge responds correctly. I do this with temp senders [ I have a set value for 80C] and it tells if gauge or sender are at fault. Benz has a temp/ohms chart for those.
I have to wait til the pressure reads off pegged cuz pegged can be anywhere above 3 bar.
We are on the leading side of a hurricane here at present, so I will see how it goes in the morning [ if I still have power/cable]