snips.... here and there.

  I bought an OBD II reader from Harbor Freight

  http://tinyurl.com/2coejqe

  when it was on sale for $49. I did get a check engine light on
  the RX8 last summer, and it turned out it was the rear O2
  sensor.  I replaced it with a "generic" one.  The generic was a
  Bosch, and came without a plug on it...guess that's what made it
  generic.  Mounted the plug from the old Mazda sensor on the new
  one... cost less than $50 from Rock Auto and an hour crawling
  under the car.

  Been meaning to ask...could the oil in the gas have caused that
  rear sensor to fail?  Or can I expect them to die around 60,000
  miles?

  Harley

  Could be the oil in the gas. How much are you adding?
  Is it 2 cycle oil? What brand?

  I have been adding a 1/2 oz per gallon. It just went through
  CA smog check with flying colors. 30,000 miles.

  That OBD II monitor was exactly what I had in mind.
  The Chinese beat us to it.

  Paul Lamar


Harley:

   Did that Harbor Freight OBD II code reader distinguish between the
front and rear O2 sensor? The reason I ask is the last one I used just
told me O2 sensor, not which one and that one cost $250. $49 or 59, now
is quite a deal.

Tom/norpro


Tom...it did mention a specific sensor, but in my opinion it got them
backwards. If I remember right,  the OBD II monitor said that O2-1, was
the problem, which I assumed would be the upstream (front) unit since,
IMO, the number one implies the first one that the exhaust stream sees.
I took the downstream one off first, as that was very easy to get to,
and tested that.  It was the downstream one I replaced, which in my
opinion would be O2-2.

As of yesterday, Rock Auto, and Pep Boys still have the universal Bosch
sensor.  It was $50 at Rock Auto and $70 at Pep Boys.

Here's a pretty good description of how they work, how to test them,
what causes problems with them, and how to sometimes repair them:
http://mr2.com/TEXT/O2_Sensor.html

Harley