Looking to get a new oxygen sensor for bae, but I'm confused about what to get. Is there a difference between the upstream and downstream oxygen sensor? The OEM ones I've seen so far are advertised as "upstream" sensors, so it seems like there is a difference between the two...but I don't see any "downstream" ones available. Here's what I see:

=4&vehicle[liter]=1%2E5&vehicle[submodel]=LX&vehicle[model]=Fit&vehicle[make]=Honda&vehicle[year]=2015]https://www.carparts.com/oxygen-sensor/denso/np2349146?&vehicle[cylinders]=4&vehicle[liter]=1%2E5&vehicle[submodel]=LX&vehicle[model]=Fit&vehicle[make]=Honda&vehicle[year]=2015

As a side note, I'm planning to start with the upstream sensor, because the voltage readings don't appear to be changing (oscillating, etc.) like they should be when I keep it at a constant RPM. Another note, my meter doesn't let me measure voltage on the downstream one for whatever reason, and my meter only shows current readings for it. Again, not really sure why.

Any help is appreciated!

 

Look on Rock Auto, they have the downstream one. The sensor itself is probably the same, but the wires might have different length...

 

I don't see the Denso downstream sensor on Rock Auto, maybe I'm just blind. On Autozone, it also appears that the sensors are potentially different, which is unfortunate. Here's what I found:

https://www.autozone.com/emission-control-and-exhaust/oxygen-sensor/denso-exact-fit-oxygen-sensor-234-4978/269751_4610_40154_98000

https://www.autozone.com/emission-control-and-exhaust/oxygen-sensor/denso-exact-fit-oxygen-sensor-234-9146/269989_562832_18264_97999