[MBZ] Using Duty Cycle to Measure ECU Codes

[John Peterson]

I am using the Sears duty cycle meter ($29) to read ECU codes on my 1990- 
trying to diagnose a no turbo boost situation.  I am putting the positive 
lead on the (+) of the battery and the (-) lead to terminal #4.  I am 
getting a 50% duty.  Are these the correct pins to use to read duty?  I have 
the MB manual of codes but I don't know which pins to read on.  Can anyone 
help?  Thanks Friends

John Peterson
Kingston, RI
1990 300D 2.5 127k
1991 300D 2.5 72k