Quote Originally Posted by LapeerGTP View Post
Ok can I get the cliff notes version of this thread for my 04gtp. I'm putting headers on and removing the cat. I'm purchasing hptuners to do all my tuning needs but I'm concerned about the cat diagnostic test. Has hptuner come up with the ability to disable it or is it not a big deal if I leave the downstream o2 in?? Sorry for the newbie question but I don't wanna spend all the money only to have the car run like sh*t


Sent from my DROIDX using Tapatalk
I have HP Tuners and last time I looked at an 04 GTP file you still could not disable these diagnostics using their software. If you can't get someone to find you the same OS with these tests deleted (using TinyTuner), then there is something else you can do.

You can choose to leave that post-cat O2 sensor installed or you can remove it. But no matter what, you're going to need to set all the DTC's relating to the catalytic converter and post-cat O2 sensor to "No MIL" and make sure the "SES Enable" box is unchecked for all of them. Doing this in HP Tuners will allow the codes to set but should prevent any check engine lights or warning messages from being displayed on your dash - and prevent the diagnostic tests from constantly running.