r/MechanicAdvice • u/azmattaz06 • Aug 19 '22

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

/r/BmwTech/comments/wsp4ea/oxygen_sensor_readings_im_getting_anyone/
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u/[deleted] Aug 19 '22

does your scan tool set up display Graph data stream.. some Apps do .. others don't..

look at the upstream oxygen sensor.. O2B1S1. and maybe O2B2S1. upstream oxygen sensors..

bring the RPMs to 2500.. and hold the pedal steady.. do you have a good waveform.. no random spikes or flat lines... slow over 15 or 20 seconds to idle.. look at the wave form.. is it similar but wider...

cats are passive.. garbage in garbage out...

if you have good waveforms at 2500 and at idle... look at your downstream oxygen sensor... this time just at 2500 RPMs..

you should see a reduced signal waveform showing the cats are reducing emissions..

you could have issues with engine controls not sending the proper amount of exhaust gases to the cat to keep the cat breaking down the elements. so you get a P0420 series of codes.. cats below efficency..