p0421

So I've had a few codes for a little while maybe 6 months and recently have been trying to fix it myself by reading this forum mainly. I've tried taking it to my mechanic but he doesn't understand what I'm talking about and jumps to replacing the pre-cat. If it comes down to it I'm fine...

Hi I am kinda new on here,ive been looking at this forumn for a while now and finallly decided to register.. ive owned my msp for about half a year, I just installed a sls catless midpipe and have just thrown the p0421 trouble code. I cannot feel any difference.in my car, it seems to be running...

Hi all, Initially, I got P0300, then I got a bliking CEL but had to drive, then changed the spark plugs and the CEL went away. But after a few miles at ca 50mph, I got a new CEL. I got it checked today and got the dreaded P0421. It might be that the catalytic converter (WU-TWC) got ruined. I...

There are several excellent posts about the non-fouler trick here on these forums. However, they require a basic knowledge of exhaust systems that I didn't have until I had to do it. While I was able to figure it out, I would have liked to have a much simpler guide available. This post is for...

I bought my P5 new in 2001, and have kept it stock ever since. I have 128,000 miles on it. A couple of years ago, I started getting the random misfires. Replacing spark plugs and wires helped, but it was replacing the coils that finally fixed it just about a year ago, just in time for me to...

My Car 2002 P5 145 xxx km Standard and stock I have a P0421 code and sometimes at idle my car will drop below 500 rpm if you give it gas its okay. I believe the computer is not controlling the air/fuel mixture properly. My manual says thats its the O2 sensors (loose or malfunctioning... they...