Hi i just purchase a 2002 p5 about 2 weeks ago..the check engine light was on for code P0421,so i did the defouler trick.The light came back on in no time,no matter how many times i reset the ecu..Do you guys think that the cat is really bad??Ive never use the defouler with the cat still in place before.Is that the reason why the light came back on so fast??Thats the only code the car have.thanks for your input.
