Good day all. I have an '04 6s with 110k miles on it. I've had the car since 05' bought from a dealer
in NY with 9k miles on it. Never had a stitch of problems other than a coil here a fresh air intake there. However, recently I have experienced the nasty P0421 code. I've read almost ALL of the posts pertaining to this issue and still do not have a solid understanding. I have NOT replaced any of the O2 sensors in the car
since purchasing it. Should I change the O2 sensor before jumping on the precat replacement bandwagon? Here are my questions in addition to the above.
1. Precat issue 0421 is bank 1 or 2 AND which is bank 1? Front or rear?
2. I plan on keeping the car and giving it to my son who is starting college. The car is completely stock. Should I just replace the precat and if so would you recommend replacing the other one while I'm under there?
3. If I were to put MSDS or CP-e headers on the car what does that do to the O2 sensors and CEL? I live in NC where they do OBD emissions tests.
4. It appears in all the posts that I've read that the header installation is relatively easy. Does the install go from the headers to the single center cat?
Thank you for your input and apologize for the redundant question.