I have not had any problems with the ASR on the '94 E320 I have and I have 211,000 miles on it. I don't know if it is the same transmission as an E420 but the way the ASR reacts is probably the same. Warning: If you live in a snowy region get snow tires because when the ASR detects slip it only gives you about 1500 rpm of engine to the tires and decreases from there almost to the point of idling. The car should have a switch on the dash or somewhere with a picture of snow chains on it and that overrides the ASR for a brief period. It can be a frustrating system performance wise on hills.

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles