My daughter has a 2001 Nissan Altima and her service engine light just came on today. I took it to Auto Zone and they diagnosed this with the troubleshooting code of P0420
OEM Brand: OBDII Catalyst efficiency low-bank 1.

What causes this and how is this fixed. I would like some kind of idea before I take it to a dealership or somewhere else... you know being a woman they will try to screw me over and tell me there is more wrong with it than there really is...

Thanks

I found this site that may help: Check Engine, Service Engine Soon light, OBD II engine trouble codes (http://www.samarins.com/diagnose/checkengine.html)