You need nothing more than a wire or paper clip to read the top and roll bar codes on a '90-'93 car, Marvin. The socket for the top controller on your vehicle is #10, and the procedure is here: http://www.benzworld.org/forums/r129-sl-class/1266535-diagnostics-sl-pre-94-a.html?

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For Sale: many used R129 parts from a white '92, black interior. Send email if interested.