Your idle pressure should be reading around 1.5 - 2.5 bar depending on the viscocity of the oil you currently use.

I've replaced the sending unit on my M104 (300E) twice. The unit costs around $65-$70 and can be replaced in less than 30 minutes.

Access to the unit is under the vehicle. A bit tight to get to as you have to maneuver around the starter and the harness. I don't remember what wrench size to use, but make sure it's a short one...not a lot of room to turn, but after a couple turns, you can hand loosen and remove.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car