i went 2 autozone 2 get my ses light off cause i just put my headers on 2months ago and tha code came up pP0421 and it reads

the pcm has determined that tha warm up catalyst efficienency for bank 1 is below threshould for tha current engine operating conditions ( bank 1 identifies tha location of cylinder #1 while bank #2 indentifies tha cylinders on tha oppiste bank

 

basically if you install any brand of header on our cars, the ses light will come on. you have to understand that you are removing the 1st cat when you switch out the header with an aftermarket one. there are 3 things you can do to get rid of the light. 1 you can try a mil eliminator (some people say is dosent work). 2 pull out the gauge cluster and disconnect the ses light bulb. 3 put your stock header back on.

 

4. Learn to live with it (beleive me, after 2 months, you won't even see it anymore).

 

^i hear ya on that one bro. i've had mine on for over 8 months now lol. i just put a gauge in front of it on my steering coulmn.