I had to replace my sensor in the W210's OM606. It uses the exact same part number as the W124's OM603. Except on the 210, there is logic in the front SAM that does not produce the warning until the contact has remained open (the switch is fail safe, it closes on good oil level and opens for low oil level), and the engine has gotten to 60C, and run for a certain number of minutes. The end result was that I was getting the warning every time I passed the grocery store 3 miles from my house +/- 500 feet from a cold start. Almost kind of spooky until I figured out why.

The 124 cluster I believe just has a simple inverter circuit that turns the light on when the contact is open (or the wire gets broken or disconnected).

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech