Nissan Repair: 01 Maxima Service Engine Soon, oxygen sensors, o2 sensors

Question
Hi,

I recently purchased a '01 Maxima (89K mi) and the SES light came on.
I have had it cleared, and it reappears after approx 30 mi of driving.
I got the code read at a local Advance Auto:

P0430
TW Catalyst System, Bank 2

I have spoken to a couple of people regarding this but have not gained any conclusive info yet.

Would you be able to advise what would need checking/changing?

- O2 Sensors
- Pre-Cat
- Cat

Also, I have gotten mixed results in trying to determine the location of Bank 2, and hence the sensors.

I obtained a diagram from Nissanhelp.com which indicates that Bank 2 is to the front of the car, closer to the radiator
http://www.nissanhelp.com/Ownership/Common/1999-2001%20NISSAN%20MAXIMA;%20O2%20S...

On searching several forums though, several people have indicated that Bank 2 may be on the other side....

I really would like to avoid changing the wrong sensors...

Can you advise on how I should tackle this problem?

Answer
James,

I would replace both front oxygen sensors.  These are the two before the back converter.  I just replaced them on my wife's 2000 Maxima SE and it runs great.  If you replace just one the other is soon to follow since they wear at the same rate.  That is, they get coated by fuel residue and it makes them lazy.  That is, they act like they are running lean since they are coated.  So, they send a signal to the computer saying they are lean and this causes the computer to richen up the mixture.  This causes low performance and bad fuel economy.