>Do they both or just the one ahead of the cat?
Think about it... why would they put a second one behind the cat, if it didn't
provide any data to anything?
BTW -- neither the O2 sensors, nor any other sensor, turns on the SES light.
The PCM turns on the SES light -- based on the data that it's receiving from
the various sensors.
I'm sure you can find loads of information on this if you Google for it.
>> > Exactly what do the 2 oxygen sensors do besides turn on the SES light?
>> >
>> Provide data to the PCM.

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Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
Oppie - 20 Dec 2006 19:41 GMT
My understanding is that the downstream O2 sensor (after primary CAT) gives
a check against the Upstream (at exhaust port) sensor. The downstream
sensors are supposed to last much longer than the upstream one. The
downsteam one also measures the effectivenss of the CAT.
>>Do they both or just the one ahead of the cat?
>
[quoted text clipped - 13 lines]
>>> >
>>> Provide data to the PCM.