O2 sensors pre- and post-cat

Steve Ravet steve.ravet at arm.com
Thu Sep 10 22:27:48 GMT 1998


Mike Morrin wrote:
> 
> 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

It expects to see no or little voltage swing on the second O2.  If it
sees swings in closed loop on the second O2 sensor, then it assumes the
cat is going bad and it sets a trouble code.

--steve

-- 
Steve Ravet
steve.ravet at arm.com
Advanced Risc Machines, Inc.
www.arm.com



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