P0420 code, replaced front o2 sensor, no cats = what else could it be???

[FLEX3269]

I have a 02 trans am that keeps throwing a P0420 code at me even after ive cleared it several times. I have no cats, i have an ory, and i just replaced the front o2 sensor the other day, i have a diablo tuner that is supposed to turn off the rear o2 when i installed the tune. So i have no idea what could be wrong?? If anyone has any ideas i would love to hear them.

Thanks, Tony

[0rion]

that's a drivers side rear O2 sensor code. Evidently you don't have them turned off with diablo. I forget how the diablo's screen was set up. Are there different options or just on and off? I would hook back up and make sure you're turning those off.

[FLEX3269]

Well honestly i cant find that specific code in my tuner to turn it off and on diablo just says that it gets turned off with their tune

[0rion]

I'm pretty sure you have to go into the "modify parameters" section and turn the codes off there. Let me do some searching real quick.

[0rion]

ok, looks like you have to go into modify parameters and turn off COT to disable that code.