Hi all,

I have a 2006 RR HSE 4.4 and the ECL came on and off for the code p0420. I know it for the cat below threshold. I replace both side with Magna Flow cat and all 4 new O2 sensors. I want to know if anyone use Magna Flow cat with the same problem. Maybe it not OEM parts. :

 

Many newer cars are very sensitive and I have had very little luck using aftermarket converters.

 

This has happened to me before on a VW, an Audi, and Jaguar. Its not the "correct" way to fix it, but it works for me. Go get a spark plug anti-fowler, it should screw into the O2 sensor. Then screw the O2 sensor and Anti-fowler into the cat as a whole. This pulls the O2 sensor out enough to still allow it to get a reading and make adjustments, but it de-sensitizes it. The computers in both Audis and VWs are very sensitive to O2 sensor readings, and their dealerships have even issued computer updates to make them less sensitive, because many times there isn't anything wrong with the cat.

I realize its not a "by the book" way to fix things, but it has worked for me. I've put well over 3k miles on my Audi, and the light still has not come back on. Prior to that, it would come on every 3 days or so.