With the ignition on but the engine not running, the duty cycle tells which version of controller is installed.
A 70% duty cycle indicates the standard controller with the ability to read some faults by monitoring the duty cycle.
85% indicates the California controller, which ordinarily displays the faults as a blinking LED on connector X92, although it can be programmed to display the faults as an X11-pin3 duty cycle.
100% indicates the controller does not display fault codes in this manner, or is faulty.

Main shows constant 97% in the static test.
It drops to 10% when RPM about 2000-2500.
Is it bad controller? The car runs pretty good on 60-90 mph.

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1987 MB260E 187K