SES Code P0420 Catalyst Problem

[SilverPathy]

I just went in to get my SES checked out and it threw code:

P0420Catalyst Efficiency Below Threshold<Bank 1>

My question is, since there are 2 catalytic converters on the pathy, how can i determine which one needs replacing? My mechanic recommends i change both, and the price he gave me was $750 for each converter (+ $40.00 to install each).

I was also wondering if replacing the OEM catalytic converter with an aftermarket high flow cat is a possible alternative in fixing this problem being that the aftermarket high flow cats cost ~ $100 and OEM cats cost $500 from partznet.com (i was overcharged by my mechanic for the part).

Thanks

[elwesso]

I would look into replacing the o2 sensors and having the TSB done first, thats a more common problem on the pathy's

Welcome to NICO!

[SilverPathy]

Thanks for the response. Just out of curiousity, if the problem was with the o2 sensor, wouldnt there be a code for the o2 sensor instead of the catalyst? Whats the TSB?