Which oxygen sensor is this?????

[19dabeast85]

My friend's 1998 Maxima GLS is getting codes:

P0325 Knock Sensor - going to replaceP0139 Bank 1 Sensor 2P0138 Bank 1 Sensor 2

Also, with my scanner, I'm seeing 3 sensors and the other 2 are switching between low-high voltages correctly, bank 1 sensor 2 is a constant ~0.05 volts (obviously bad)

My question: Which sensor is "Bank 1 sensor2"??

Thanks

[MinisterofDOOM]

Welcome to NICO!

Bank 1 is the rear bank. Sensor 2 is the "rear" one (furthest back on the exhaust).

[19dabeast85]

Thanks....so there are 2 pre-cat, and only 1 post-cat? I'm used to 2 pre & 2 post, but w/e.