I tried it. You have to do it with the engine off, but key in ignition. Indicated a single flash, meaning no codes stored (turned out the Haynes Manual at the local autoshop described the procedure). Sort of neat to be able to get the 411 without needing a code reader. Wonder why they only included this feature in the CA emissions version of the cars and not elsewhere.

__________________
Der Panzermann und Fraulein Fahrvergnuegen

1991 420SEL 201K "The Big Blue One"
1985 300DT 205K chassis/285K engine nee California emissions "Goldbug"
1983 300TDT 255K "The Womble"
1983 300 DT 214K "Sea Sprite"-Rear-ended a truck
1983 300SD 285K "The Donor" Gave his life so that others can live
1980 500SL Euro 105K "Der Panzer"