Hi all,
On the 2001 Maxima SE, I checked all 4 sensors with my scope and the bank 2 upstream was cycling constantly from .1V to .9V at idle (not sure if that's right), while the downstream on that bank was steady at .28V.
The bank 1 (firewall side) showed the upstream holding steady at .24V while the downstream was at .3V. That would appear to be ok...I think.
Once I ran the motor at a couple thousand RPMs and reved it up and down, the bank 1 downstream (or maybe it was upstream...I'm confused as heck) was at .1 to .7. Now when I went back to check the bank 2 sensors, the upstream that was cycling constantly before was now more steady at .3V.
Does everything appear to be ok. The car HAD been setting the po420 code, and after it being driven today and tested tonight, it had no codes at all.
The reason for the above mentioned confusion is that upstream sensors are supposed to cycle between .1 and .9V and I am assuming that the sensors that are up at the exhaust manifolds are upstream/ precat. Now on the firewall bank 1 the sensor that is at the exhaust manifold is holding fairly steady while the one that is mounted on the cat is cycling.
Confused? I think I am.