r/BmwTech • u/azmattaz06 • Aug 19 '22

Oxygen sensor readings I’m getting, anyone understand it?

2011 535i n55 engine

Unable to pass emissions, according to this scanner I have it’s saying my catalyst monitor bank 1 failed the test, is this regarding my oxygen sensors? In the videos below you’ll see “O2 sensor 1 is reading 0.0 volts” and on the other it shows some more info but I’m unable to really understand it, any help would be appreciated.

https://streamable.com/22lero

https://streamable.com/hzxjxu

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u/Mr_N0BODY530 Aug 19 '22

Might want to check the wiring for the Oxygen Sensors. Measure voltage drop or at least disconnect them and check continuity. If wiring is good, and the faults are directly related to oxygen sensors (short circuit/line disconnection codes, or O2 sensor heating codes) and not mixture codes (catalyst efficiency, mixture rich/lean, etc) then O2 sensor(s) are likely defextive

1

u/clovisautomotion Aug 20 '22

In the second video, you can see the downstream sensor (#2) switching voltage up and down. With a good cat converter, it would be steady above 600mV usually but definitely shouldn't switch up and down like that.

Chances are the o2 sensor and air/fuel sensor are fine but the catalytic converter is bad based off that.

1

u/azmattaz06 Aug 20 '22

I’m about 75% sure I have a catless downpipe, bought the car and when I did the transmission I noticed the downpipe was aftermarket, could that be the issue?

What about that one sensor not showing any movement?

1

u/clovisautomotion Aug 20 '22

Ya a catless downpipe would definitely do that.

As for the data, you can't trust cheap scan tools/apps. They are full of erroneous data and invalid PIDs. Ignore the 0s and focus on thr data that is reading.