This happens to EVERY W124.

No need to take dash apart, there are special tools.

A professional can have this fixed in less than a minute, and many will have a "loaner" lock cylinder to give you until your matching key version arrives from a dealer.

Since the labor involved is so little, this is a job where DIY doesn't save much.

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles