Bought a hand held code reader and saw that the bank 1 o2 sensor was gone. So I replaced it and it didn't work, only later to find that it was because of a broken ground wire on the body of the car under the battery. So I fixed that and all was good. Saw the light come back on again and it says the same thing. What else can be tripping this? Can the catalytic converter cause this? I bought a new Magnaflow one 3 years ago. Any ideas?

The sensor I did buy was brand new from the dealer too, not aftermarket.

 

P0420 is the "post cat" O2 sensor reporting cat is inefficient.
Cheap fix :http://forums.clubrsx.com/showthread.php?t=296791
$6.00 fix for certain P0420 & P0432 codes