O2 Sensors? I need help! PO422/PO420????

bronson1111 · Post by **bronson1111** » 12 May 2011, 15:44

I have a 2002 Volvo S80 T6 and my check engine light is on. I had the codes checked by four different mechanics and they all said it was a PO422 and a PO420. Basically both are to do with the catalytic converter efficiency. I tried to do the spacer/nonfouler trick to get the CEL off but it didn't work. I looked at the two O2 sensors near the CAT and they looked kind of blackish. Maybe I need O2 sensors? Would bad O2 sensors set off a PO422/PO420?

THANK YOU!
Bronson

Post by **dcarlson12** » 12 May 2011, 16:58

My understanding is that a catalytic converter can be 'killed/damaged' if the vehicle runs in open loop mode for an extended period of time. i.e. it gets flooded with a rich mixture of fuel
Did you have any other codes or ? previously?

I have attached a page from VADIS which discusses the three way catalytic converter.

Not sure if you can get the converter to come back to life by just driving at high speed for an extended period of time to try to really heat it up to maybe burn off any soot or other residues which might have reduced it's efficiency.

If you are saying that the O2 sensors downstream of the converters are black/sooty, I believe this would confirm that you have been running rich.