I've read the forums about the O2 sensorsi was wondering if anyone can help me out with where to buy them and how many wires each one has i called a place and they ask me for that info thanks in advance

 

http://www.bentleypublishers.com/tec....dtc.table.htm

P0421 isn't on that chart. Are you sure it has anything to do with O2 sensors?
Your O2 sensors have 4 wires by the way, and you can get them at www.ecstuning.com or www.purems.com

 

Warm Up Catalyst Efficiency Below Threshold (Bank 1)

P0421 is an emissions code for sure. i assume your using OBD II.i have a smiliar one because of my test pipe.

quick fix is change your spark plugs.. on might be fouled. or if not your 02 sensors are damaged. the secondary most likely. reading the "supposedly" fresh minty air you cat spits out. if that is the case you got to think further about what damaged it in the first place..... maybethe cat? what your mileage? check engine i assume? rough idling?

02 sensors are availbale at ECS tuning.com as auditech said.
good luck