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#13: 02-06-2013, 05:43 PM
Title: Contributing V.P.
Location: Milwaukee
Car: 99 Legacy 2.5GT Toyota Supra 2jz/R154
Posts: 1,048
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Being a Toyota certified master tech and ASE Master Tech with 15 years in the biz I can tell you that Japanese and Euro cars have much higher quality cats made from gold and platinum and should never go bad unless someone's drives with a cylinder misfire for a while and a while I'm talking a year. American cars have much cheaper cats being made of mostly rhodium with small amounts of platinum which will fail quite quickly with a cylinder misfire. Like I said above check the o2 data and also for a exhaust leak. They both will cause a P0420. I believe there's 3 o2 sensors on our cars. Also 96 Subaru Legacys with the 2.2 will pass emissions without the monitors being fully reset. I know this because I owned one and couldn't figure out why my cat monitor wouldn't set so I logged in the EPA's website and found a list of OBD2 cars that do the same thing. Check the rest before replacing the cat and I also I wouldn't say all aftermarket cats are junk. Bosal and Magnaflow cats are actually good cats just to name a couple.