TANTO Posted June 30, 2011 Share Posted June 30, 2011 2001 RX300, 80k miles, getting P0420 "catylist efficiency below threshold". As i have a hard time believing i have a bad cat with this mileage, I'm thinking about replaceing the rearmost A?F sensor, and then perhaps the others also. Comments please? I noticed there are several sensor brands available. Any of these to stay away from. First post. TIA Quote Link to comment Share on other sites More sharing options...
DEATH_AWAITS_YOU Posted July 6, 2011 Share Posted July 6, 2011 2001 RX300, 80k miles, getting P0420 "catylist efficiency below threshold". As i have a hard time believing i have a bad cat with this mileage, I'm thinking about replaceing the rearmost A?F sensor, and then perhaps the others also. Comments please? I noticed there are several sensor brands available. Any of these to stay away from. First post. TIA Don't replace your A/F sensors. The problem is with your converter(s). Unfortunately, the early models didn't differentiate which of the three converters was at fault. You can try one at a time or just forget about it. Don't know about emission testing in your area. People usually get very discouraged when I tell them it may be any one of three very expensive parts. Quote Link to comment Share on other sites More sharing options...
jaswood Posted July 9, 2011 Share Posted July 9, 2011 2001 RX300, 80k miles, getting P0420 "catylist efficiency below threshold". As i have a hard time believing i have a bad cat with this mileage, I'm thinking about replaceing the rearmost A?F sensor, and then perhaps the others also. Comments please? I noticed there are several sensor brands available. Any of these to stay away from. First post. TIA Have you recently had a period, even brief, or TC or VSC activation..? Those use EFI fuel starvation to dethrottle the engine leaving "pure oxygen" reaching the catalyst. Mine will clear those codes in 50-100 miles. Quote Link to comment Share on other sites More sharing options...
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