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04 Highlander v6, 180000 miles, about 3 weeks ago got code p0430...cleared code. Today as I was traveling about an hour on I44 (avg 75 mph) ck engine, vsc, and trac off appeared (same as 3 weeks ago). Ck with scanner and again same code. States Cat Syst efficiency below threshold bank2. Drove 420 miles between the lights coming back on.
If it has a problem wouldn't the lights immediately return after clearing and not take 3 weeks?
Owned the car 3 years .
What your thoughts.
thanks in advance
 

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your cat could be borderline and is only tripping the code during certain conditions. I had the same problem and the code would stay away for a couple of weeks, but gradually came on more often until it would come back the same day. I had over 200k miles so i didn't want to buy new cats so I tried o2 sensor extenders. They don't fix the problem, they just make the o2 sensors less sensitive. I have had them on for well over a year now without tripping any codes! The only problem I can think of is if your cats become clogged, but if that happens to me they will just get hollowed out. To do this you will need one straight extender and one 90 degree extender to make the rear sensor clear the firewall. I forget the exact price, but they are something like $15 or $20 for stainless ones on amazon and take about an hour to install depending on how hard your 02 sensors come out.
 

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Interesting to know. I have been getting P0420 codes, again intermittent initially but now VSC lights on permanently (212,000 miles). Why the reluctance to change the cat?
 

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Generally the reluctance is because Non oem cats are generally junk and only last 2-3 years. And oem cats are way expensive.
 

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yup, it was basically a cost vs. benefit thing for me. new jersey doesn't "sniff" the exhaust for emissions tests, they only check for codes. therefore, since it doesn't affect safety, mileage, or performance to replace the cat I went with the much cheaper option of extenders. I figured it was worth the couple of dollars to try them before spending $500 - $800 for inferior aftermarket cats. As I said earlier, if my cats start to affect performance or mileage due to clogging, I'll just hollow them out.
even with the cats running below threshold the exhaust doesn't have a smell, so I don't think they are even that bad, just not up to snuff for the computer.
 

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Thanks for explaining, very helpful. Down here in SC no sniffer tests, no code checks, no nuttin! Think i will look into the extenders as the dash lights are beginning to get to me
 

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There's always the black electrician's tape option, has effectively removed the TPMS light that was irritating me.
Indeed, and it may come to that but trying to avoid at the moment. Got a quote from the local independent garage - $120 to tell me what is wrong and what P0420 means. Think i will get the extenders and see if that sorts it.
 

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one thing I forgot to mention. The extenders come with a straight thread, so they need a crush washer as a seal. The ones I ordered came with rubber o rings. needless to say, I went to the auto parts store and bought some copper crush washers. I forget the size but you can google o2 sensor thread size.
 
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