Bank 1 Sensor 1 O2 Sensor (P0131)

[BOARF16]

The day after a long car trip, the car started to hesitate/buck under light acceleration between 1200-1800 rpm. This happened in both manual and auto shifting modes. When the car starts to hesitate/buck, the mpg gauge fluctuates as well. If you use moderate/aggressive acceleration, the car does not hesitate/buck.

2 days after the trip, hesitation/bucking is worse (still under light acceleration and low rpm) but it now tripped a CEL with a P0131 (Bank 1 Sensor 1 O2 Sensor low voltage).

There are lots of pictures and DIY of the N54 motor but I have been able to find a lot about the N55. This is what I am trying to confirm:
Please reference this picture:

The N55 has only 2 O2 sensors, Sensor #1 is the Pre-cat sensor which is labeled as Upstream Sensor INDEX #1 and Sensor #2 is the Post-cat or Sensor after ceramic structure INDEX #6). Is this correct?


Has anyone else had these symptoms? Could the O2 sensor be the only culprit.

Thanks!

[Cattivo]

Not sure if the N55 has only 2 02 sensors or 4(pre cat/post cat)...My best advice would be to replace both bank 1 and bank 2 upstream 02 sensors...down stream rarely go bad

If the code doesn't go away try adding some cataclean...your cats may be clogged