W140 Sensors testing
 

Does anyone knows if the sensor for oil level light is normally open or closed to ground? Normal oil level opens and low level closes?. Do all the MB sensors work with the same principle?

Normally closed
 

From Alldatadiy:

The oil level is measured with a float (6) with ring magnet (7) and a contact
If the engine oil level is not sufficient, the contact (arrow) opens. the vehicle ground to base plate in the instrument cluster is interrupted and the indicator light (A1e12) comes on after a time delay of 60 seconds The time delay of about 60 seconds prevents the indicator light (A1e12) coming on if the car is accelerated or braked sharply or when cornering

Memory
 

Does the warning light have memory, or it should turn off as soon as the float goes up? If I shortcut the pin connector to ground, light should turn off, am I correct?

Never done it, but that's the way I read it.