oxygen sensor query

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oxygen sensor query

Post by PeterM » Mon Nov 09, 2009 4:06 pm


If a zirconia o2 sensor complete waveform is biased towards the rich [low in o2] in closed loop and the ecu leans out to maintain the A/F ratio, how come the o2 waveform appears to stay the same i.e. still showing a rich reading at a steady 1500rpm.

Appreciate any help offered.


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Matt Fanslow
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Re: oxygen sensor query

Post by Matt Fanslow » Mon Nov 09, 2009 4:43 pm

Can you verify with an exhaust gas analyzer that the trim adjustment "worked"?

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Re: oxygen sensor query

Post by Autonerdz » Mon Nov 09, 2009 4:48 pm

Hi Peter,

Not sure I fully understand the question. Is the O2 voltage always high, or does it switch normally and just spend more time high than low?

If it is still switching but biased high by spending more time high than low, this could be normal strategy.

If it is high and not switching, even with fuel trims negative in closed loop, then probably the O2 has a problem or the PCM can't compensate.

Tom Roberts
(The Picotologist)
skype: autonerdz
THE PicoScope Automotive Authority
In North America

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