duty cycle readings ?

[Ameer Antar]

in closed-loop, the duty cycle changes b/c the o2 signal is going up and 
down. The rate of change for the duty-cycle is about the same as the change 
in the o2 signal, although there is prolly some delay b/c of the ECU 
electronics. So if the o2 sensor signal just happens to be bouncing around, 
[which I know it does, I've seen it on an afr gauge], the duty cycle will 
too...no problem w/ your ECU. In open-loop however the D.C. should be 
fixed. If the o2 sensor is more than 30k miles old, I'd change it, or less 
miles if you burn oil or have a rich mixture. Oil and rich mixtures build 
up deposits on the sensor, making them short-lived. I think heated o2 
sensors have a longer life, something like 60k for newer designs. That may 
explain why you get a difference of in duty cycle frequency compared to SJM 
info.


At 04:15 AM 12/16/2000 , you wrote:
>Hi all.
>I am posting this question 3rd time. No response yet. Hope never dies.
>
>According to SJM ECU changes duty cycle in closed loop 1-2 times per
>second.  I see that duty cycle is changed much more frequently (10
>times, maybe more). In DMM screen I see blur. I wonder is my ECU doing
>wrong things? But it sweeps in spec: 45-50%. In several minutes it
>shifted to 40-50% but it is another why?.
>
>OXS voltage mesured by DMM is between 15mV and 2.2V. Does someone has
>any idea why it can be more than 1V according to spec? (I did not
>disconnect OXS wire while measuring voltage).
>
>Do I need to plan OXS changing?
>
>Thanks.
>
>Konstantin Bogach
>200tq 89