It is my impression they all have a duty cycle reading. The only thing they might not have is fixed duty-cycle fault codes. The duty cycle on the pin #3 goes all the way back to K-jet w/lambda cars starting in 1980. Also some later KE cars require turning on diagnostics with the diagnostic connection on the right side before a duty cycle can be read.

I do NOT like the concept of looking at this with voltage as this only works as a ratio of voltage read to battery voltage thus 6v might be 50% one time and 7v be 50% another depending on battery voltage.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician