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


Any time over 50K miles the O2 is suspect. The above procedure to test the
sensor is good. To verify the wiring, use a jumper. You can hold the sensor
wire (the one you measured the voltage in) with one hand and alternately touch
the battery posts with the other. Your body resistance keeps too high voltage
going to the ECM, but will drive it high or low if the wiring is good.

Dale Davies