just got new catalytic converter and still get p0430 code in 2002 tahoe.

[cousinwaylon]

is o2 sensor to blame? i just spent $650 for a new catalytic converter on my 2002 chevy tahoe. replaced the entire system so both cats are new. about 5 miles down the road, the p0430 code came back on. could this be bad oxygen sensors? which one should i replace? downstream or upstream? i got an engine diagnostic check that told me the cat on the passenger side was bad but due to location, the muffler shop couldn't cut it out and had to go the expensive route. any thoughts on what i should do now would be great.