I have a 2003 mp5 and I just installed header and removed the cat off of the header and now I am throwing a check engine light for precatalyst warm-up. What can I do to fix this? I have heard rumors of the fake-out o2 sensor. But I am unable to find any concrete info about it. I was informed that when I finish the exhaust system and remove the second cat and have the code cleared, it will not turn the check engine light back on. Any helpful suggestions are appreciated!

 

you can either get an MIL for the second o2 sensor or do the no-foul trick. i will find some info on both. i just bought an o2 sensor for mine that already had the MIL attached.