here's a link to a thread I'm adding to over the next few weeks around that old chestnut - the Oil Sensor in the M112 engine sump.
Oil level light intermittently comes on, bad sensor? - Benzworld.org - Mercedes-Benz Discussion Forum

I'm replacing mine shortly when I drop the sump. Repalcement was $109+post from autohausAZ - mgiht be able to get it cheaper elsewhere. the Autohause part was an original MB part - A 0061532728

Anyway - see link for a pdf on function of the unit (temp, level and conductivity) and Work Instruction sets from WIS on replacement. I will post additional pics in that link when I do the change out.

b22b