Cant Adjust Duty cycle????
 

On my 124 300e I went to adjust the duty cycle at the adjustment tower and the duty cycle is stuck at aprox 90% no fluctuation very steady 90% ,also at higher rpm it is the same it only moves during throttle movement and floats right back to 90% and stays there.
SO I tried the adjustment and nothing even at a half turn rich and a half turn lean nothing but 90% duty cycle?
Then I disconected the o2 sensor and it went to 50% duty cycle but steady 50% no movement.I tested all this at operating temp including the o2 sensor which is at a fixed .053volts. Plug the o2 sensor back in and we are at 90% again.

Before I started the car I did the static tests with ignition eng off and it shows 70% duty cycle static.
depressing the airflow sensor plate gives us around 15%.
and full throttle gives us 24%
Mercedes wis documents show a non fluctuating 90% is current to EHA is implausible......... could I have a bad EHA or just wiring??????:confused:

Similar problem I had with my 190E, I could not adjust duty cycle. Culprit was the O2 sensor

Items responsible for adjusting duty cycle? - Page 4 - Mercedes-Benz Forum

wiring
 

ringing out wiring today. everything worked fine (well with just a rough idle and a little hesitation) untill I messed with the fuel distributor and the airflow sensor. I think the new airflow sensor has a bad pot for the plate deflection

test results
 

wiring ohms and voltages check out from the computer N3. threw in my spare fuel distributor,same problem,threw in my spare air mass sensor assembly,no help! threw in my spare EHA and still no joy:confused:
suspect the o2 sensor it seems to run better when its disconected. Every time I reconect the o2 sensor the duty cycle slowly creeps form 50% to 90% everytime! I think it may be shorted because it only creeps when the 2wire heater connector is reconnected the single wire sensor being connected causes no change:(

holy smokes these o2 sensors cost more than the ones on my 129............I may get a generic bosch one they look alot cheaper. just some terminal crimping