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Discussion Starter · #1 ·
I have a 2008 Altima 2.5L with 150k miles. It just pushed a P0420 code. I have done a lot of research on this forum and others and it seems in the older models a precat failure could cause debris to be sucked into the engine causing engine failure. I have not found any reports of this happening beyond 2006. but I want to fix the problem none the less. I read how to check O2 sensors to verify failure. the spec is to see S1 fluctuating quickly between .1 and .9 mine hangs around 2.0-2.4 v. which seems bad. And to see S2 fluctuating slowly around .5 volts. and mine fluctuates between .2 and .8 fairly quicky.

I also have a 2010 altima 2.5L with 80K miles and no DTC codes so I tested that and I see similar results but S1 fluctuates between 1V and 5V

I am not sure what Lambda B1S1 is but it hangs around .99 and Short term Fuel Trim stays between -10 and 10 per spec.

In your experience what should S1 and S2 look like on these cars?

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