O2 sensors pre- and post-cat

[JRECPA at aol.com]

In a message dated 9/10/98 1:55:06 PM US Mountain Standard Time,
mikem at southern.co.nz writes:

<< If standard O2 sensors only work at a single O2 %, and the cat itself is
 changing the O2 concentration in the exhaust stream, and the ECU is cycling
 the pre-cat sonsor around its optimum ratio, then what does an ECU expect
 the post-cat sensor to be telling it?
 
 Just curious.
 
 Mike
  >>
Try this example on for size

If you have a misfire in one of the cylinders you will have excess O2 before
the cat but not after the cat.

James