P0420 Code

[Billjax]

Just started getting this code on my 02 A4 with 42k miles, Blackwing and Z06 catback. I reset it and it goes away for a day or so, until, I suspect, the right driving conditions exist for the test to take place.

Are there any simple tests I can perform to confirm that the cat is shot or if it might be something else?

I have GMPP Major Guard so between that and the federal warranty, I guess I should be OK.

TIA for any input!

 

[wishuwerehere82]

Some diagnostic help on reading voltages and deciding if it's a serious problem.
http://www.forparts.com/IC3wayconverter12.03.htm

 

[Mr. Lucky]

DTC P0420 (or P0430) - Catalyst System Low Efficiency

Your driver-side rear O2 sensor is not reading a sufficient difference from the front sensor. You could have a bad sensor, bad catalytic converter, or an exhaust leak in that area. Troubleshooting procedure here.

GL!