Original so it had to be done eventually. Oil level sensor isn't that expensive or hard to do. E420 is one of the easier lower oil pans, maybe 20 allen bolts, no clearance issues, need a new pan gasket, a little extra torque when you put it back. I think it calls for 6 ft. lbs, better to do about 8. Inspect and clear your oil pump intake pipe screen while you're there.