Over the last couple months as I browsed this forum I saw numerous references to a service CD and my curiosity is piqued. Exactly what is this CD? Is it a factory authorized service manual on CD? Or is it produced by a third party? How valuable is it (if at all)? Does it cover in-depth troubleshooting such as fuel injection and climate control, or just basic remove/reinstall procedures? How does it differ from Haynes/Chilton? Finally, how/where do I get one, and how much does it cost?

I tried using the search function with "CD," "service CD," etc. but keep getting no matches.

Thanks in advance!

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280