I just change the oil on my wife car and I could not reset the FSS warning. I have done this many times in the past, but this time I am about to give up.
The car is E320 1999

and this is the instruction I used

1- Turn electronic key in steering lock to position 2.

Within 4 seconds press button "0" twice.

2- The present status for days or distance is displayed. Within 10 seconds turn electronic key in steering lock to position 0.

3- Press and hold button "0", while turning electronic key in steering lock to position 2 again. The present status for days or distance is displayed once more. Continue to hold button "0".


After approx. 10 seconds a signal sounds, and the display shows 10 000 miles (Canada: 15 000 km) for approx. 10 seconds.


4- Release button "0".

 

is is occasionally reported that the DOORS must be closed. i dunno...worth a shot, eh?