Originally Posted by
Buster1949
I replaced all four O2 sensors on my 2011 328i but can't fix 29f5, what should I do next ?
Signal, Oxygen Sensor, bank 2 after Cat is swinging from .74 v to .06 v ? this drops off in one reading to .06 and then returns in a couple of seconds to .74. The old o2 sensor was indicating the same dips as new sensor .
Signal, Oxygen Sensor, bank 2 before Cat reading 1.93 v to 2.07 v
Bank 1 before Cat 1.96 v
Bank 1 after Cat .72 no sudden dips
Does the above dips on bank 2 after Cat indicate a plugged or damaged Cat ?
At idle the engine should switch between running lean and rich for emissions purposes because it keeps the cat working in an optimal range. You should see that on the pre-cat o2, but not on the post cat o2. The cat should smooth it out if it is working. I would expect to see a flat value on a post cat o2 signal if the cat is good. A cold cat doesn't do anything so you should let the cat warm up and look at the values again before calling it dead.
If the car can rev freely and doesn't have issues running you don't have a plugged cat.
I have both N52 cats for sale if you happen to be in SC anytime soon.
Mechanical Engineer, Automotive Engineering Student, and Ex-BMW Intern
2009 E91 335i conversion
2003 W220 Mercedes Benz S600TT
GM 2500 Coming Soon
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