I can not understand why it is so hard to find any online Fault Code information for the 85 Mercedes 500sel. Any help/links to find these fault codes and explanations of codes found in a diagnostic test would greatly be appreciated. Also, any suggestions on an inexpensive, decent, diagnostic scanner (OBD1 standard I believe), even used?

Thanks.

The 85 500SEL does not support ODB1. Mercedes prior to 1996 really didn't adopt the ODB1/2 standards.

There is some limited fault information available via the CIS control unit however I'm not that familiar with the unit on the 85 model year. If its the same as that on the 86+ car then you need to read the duty cycle at the X11 port (pins 2/3).

If the value is bouncing around then the system is operating normally. If the value is stuck a certain percentage (after about 1 min of engine running) then the system is indicating faulty component.

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