Key in the 1 position. 1.5mm pin, paper clip or allen works, but it helps to grind an edge to an angle to help it slide over the keeper. I used an allen the first time, hard. Picked up a pointed probe at Radio Shack the second time, easy. Once you depress the keeper, unscrew the black retaining ring. I had to use long needle nosed pliers, scratched up the collar, now have the official removal tool for next time. On reassembly, make sure to align the collar correctly or the tumbler won't turn. If you get in that position turn the collar until the keeper clicks into the slot. By the way, if you put the tumbler in without the collar and turn the key to the zero position, the steering lock will come out with the ignition lock. Requires removal of the whole steering lock assembly, lots of tinkering to figure out how to get it all back together....been there. Much easier the second time. Good luck.

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Earl McLain
'02 C230 Kompressor
'89 560 SEL "Frau BlueCar" (retired April 2004)