Seeking confirmation: Mercedes and duty cycle

[Stretch]

G'day Folks,

I'm having a miserable time trying to diagnose a now consistent stalling problem on my W201.

{
After you drive the car the engine wants to stall when you dip the clutch. Start the car and rev from idle it is fine. I can't reproduce the fault that way.
}

So Looking at the WIS / FSM information I have for this piece of **** I see that there are two ways of measuring fault codes.

Way #1 =>

Blip code tester. Plug it in. Get a red light. Press the button for about 2 seconds - count the error codes as they come back.

I always get one blip = everything OK mate!


Way #2 =>

Ignition on - engine not running.

Measure duty cycle at X11 port (On W201 next to ABS pump left hand wheel arch engine bay)

Pin #2 is ground

Pin #3 is output from O2 sensor => duty cycle

For this I measure a 30% (29.8%) error code.


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Checking in the WIS / FSM information I've got that says temperature sender (from coolant). There is nothing wrong with this part of the car - I am totally sure about this. I get a reasonable resistance reading from the sender and I can trace this resistance all the back to the ECU plug. (Between pins7 and 21 on the ECU plug)

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HOWEVER (!)

I remember reading somewhere that Mercedes "duty cycle" is the inverse of normal duty cycle. So 50% is always 50% but 30% is 70% (20 is 80 - 10 is 90 etc etc etc)

Can some one confirm?

Anyone know?