So I Just spent most of the morning searching to finally find it, So hopefully I can save someone else their time.

W163 Service indicator reset
(wrenches) after completing Service A and or Service B

Turn the ignition key to position 2.
Immediately press the button next to the display (Left side) twice within one second. The present status for days or distance will be displayed.
Within 10 seconds, turn the ignition key to the 0 position (off).
Press and hold the button while turning the key to position 2 again.
The status for days or distance will be displayed again; continue to hold the button.
After 10 seconds, a signal will sound and the display will show 13,000 miles. Release button.

I have a 2005 ML500 and this worked for me, Honestly the timing thing is imperative, I think I got it on try 3.... So be patient

 

Thanks for the info. I'll get it try on my next service

 

No Problem!