Hi, i recently started getting a p0156 which is "bank 2, sensor 2" oxygen sensor.

Part numbers online all refer to upstream / downstream, left/right. I know I'm looking at downstream (past cat converter), but cannot figure out if bank 2 refers to left or right.

Denso 234-4400 is downstream left, while denso 234-4509 is downstream right. Can someone advise??

RX450h, 2010, 70k miles.

Thanks

 

If you're looking from the front of the engine, I think the left side would be the front side of the car, which would mean bank 2, sensor 2. Why would there be different oxygen sensors for each side...

 

Bank 1 refers to the side of the engine where cyl #1 is located.
Viewed from the front of the car, Cyl#1 is on the left side to the rear.

#1 #3 #5

#2 #4 #6

Front of RX

 

As much as I would like to think the car is smart enough to tell you what to replace be giving you a code, its not.
All the code tells you is that the voltage value is out of normal range. It may be a bad sensor. It may be a bad connection. It may be a loose sensor or bad gasket(air leak). My point is that it may not be as simple as replacing the sensor.
Hope this helps.

 

The difference between the two part numbers is harness length.
234-4400 is 10.08 in.
234-4509 is 25.59 in.

Good luck!

 

Upstream Front B2S1 – NTK 24837
Upstream Rear B1S1 – NTK 24827
Downstream Front B2S2 – NTK 24677 or Denso 234-4400
Downstream Rear B1S2 – NTK 25721 or Denso 234-4509

Also, the bank 2 sensor 2 locates in front of the car just above the cover Which is right behind the front bumper.