Setting both P0420 and P0430 at the same time

[landshark]

hi,

Have a 2004 S80 T6 with 120K on the clock.

I have done some of the routine stuff-

Timing belt was replaced. Just replaced spark plugs, air filter, fuel filter. Front and rear brakes, Akebono pads all around. The car runs great, drives great.

BUT- Both P0420 and P0430 codes get set every 40 miles or so. Always both codes. Never just 1. New plugs and filters didn't help.

The cat on this thing has 3 converters, 1 on each turbo and 1 after the two pipes come together. I understand the codes mean converter efficiency, but I don't want to replace the cat ($1000+) unless that for sure is the problem.

I just got new upstream O2 sensors, I may try that. I'm thinking backpressure tests may be next, but I'm not 100% sure.

If you have dealt with something like this I would appreciate hearing your experience. If it's the cat for sure I'm tempted to just gut it and run like that.

Any help is much appreciated.

Thanks in advance!

[mikealder]

You say you have replaced the two pre-cat probes, did you use genuine Bosch or Denso probes? if you used a generic probe then that is probably your issue as these cars are really "picky" when it comes to type of probe - Mike

[jimp54]

I've been dealing with the same codes for 6 months,just replaced all 4 02 sensors today and so far no codes,but not convinced until it's out for a few days.I get it every 40-50 miles also.Did you ever resolve the problem?

[jimp54]

I've been dealing with the same codes for 6 months,just replaced all 4 02 sensors today and so far no codes,but not convinced until it's out for a few days.I get it every 40-50 miles also.Did you ever resolve the problem?[/b]

[Stewart91]

Ever resolve this problem????