help with P0420 please
after reprogramming the wifes trailblazer with the the tune i listed on another thread in this forum, i finally got around to putting the cold-air K&N intake in and redoing the exhaust.
i cut out the cat & everything behind it (there were some nasty crimps in the tailpipe). i then replaced everything with 3" including a 3" magnaflow muffler.(the post cat O2 sensor is still wired up and in place)
Sounds awesome (the wife hates it & i will be adding a 3" resonator where the cat used to be to bring down some of the in-cab drone)
I thought i had turned off all the switching in the first tune to eliminate any codes thrown by removing the cat, but i guess not.
i keep getting P0420 codes, what am i missing????
here is my latest tune
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