Location of oxygen sensor bank 2?

So I picked up a Scangauge to check the o2 sensor voltage due to a CEL P0420. I was able to pickup a voltage on Bank 1 sensor 2, but did not receive any feedback on Bank 2...what sensor is bank 2 on?

 

Alright after reading some more I figured out there is no Bank 2 for the Gen2 Prius.

Bank 1 Sensor 1 = Upstream (pre-cat)
Bank 1 Sensor 2 = Downstream (post-cat)

So the SG2 was able to detect the downstream o2 sensor, but no values were detected for the upstream o2 sensor.

Does anybody know the location to access the upstream o2 sensor?

Thanks,
Anthony

 

Awesome!

From the looks of it, seems like B1S1 is not accessible from the engine bay at all. I assume the sensor end can be accessed under the car, and the plug within the interior cabin?

I want to first check to make sure the harness is plugged in before I order a new air/fuel sensor.

I'm also looking at the Denso as a replacement (DENSO 234-9056 Fuel To Air Ratio Oxygen Sensor).

Any tip would be great.

Thanks again,
Anthony

 

I checked under the car today and it looks like I might be able to remove the air/fuel sensor from under the car, but unplugging the harness might be an issue. The TechInfo calls for draining of the HV coolant and removal of the inverter which will be quite a hassle.

The air/fuel sensor physically looked fine, the wire was still intact and it was indeed plugged in. Is there a fuse that I should check that might be blown? Is there any other reason that the SG2 cannot read anything from the air/fuel sensor (B1S1)?

The post-cat (B1S2) o2 sensor reads between .7 and .85 voltage on average...so those values I believe are within range and the catalytic converter is still good.

Thanks,
Anthony

 

Thanks but I already read that and if not all air/fuel and o2 sensor threads.

Check the ECM voltage on both E5/23-28 and E5/22-28 and they were within specified range. That rules out a bad ECM and/or fuse I believe.

 

I'm going to have a friend/mechanic use his own scan tool to see if he can pull a value from the air/fuel sensor. If not, then I will be replacing it with a DENSO 234-9056.

Just wondering though, are there any symptoms that comes with a completely non-functioning air/fuel sensor? I've still been averaging ~43mpg without even trying to be conservative.

Thanks,
Anthony