I ha e been dealing with a P0420 catalyst bank 1 below efficiency code, which is keeping me from passing emissions. I reset it, and after 2 hours of driving git comes back. My scanner reads as follows:
Fuel sys1: Ol-drive
Fuel sys2: Ol-drive
Calc load: 2.9%
Ect temp: 182
Stft1: .8
Ltft1: 14.2
Stft2: .7
Ltft2: 11.2
Rpms: 587
Map:10.6 hg
MAF: .6 lb
I have cleaned MAF, replaced map (wore seal), replaced all vacuum lines (dry rotted), replaced pcv, new upper intake and throttle body gaskets, cleaned throttle body, new bank 1 O2 sensor. Any ideas???? I'm stumped. It drives and accelerates great. Please help!!!

 

Read this and then ask questions you may have

In the most simple sense, a PO420 means post converter O2 sensor is appearing to react too quickly when compared to pre-converter O2 sensor, indicating degraded catalytic converter performance.

https://blazerforum.com/forum/diagno...plained-19820/