The dealer gave me the print out that says:

TW CATALYST SYS-B1
[p0420]

He did something to turn the light off but 2 days later, it's back on.

 

here is a copy of the TSB . this should outline what they did or should have done. sometimes the update of the ecu does not cure this code and the main cat ends up having to be replaced. realize both the update and main cat should be covered under 8yr/80k federally mandated emiissions warranty.