godzillatreat Posted June 1, 2009 Share Posted June 1, 2009 Hey everyone. I have a 99 ES 300 with 125000 miles. I had the code p0420 a few months ago. I replaced the back o2 sensor and cleared the codes. About 70 miles later the exact same code came back on. I have searched previous posts stating that it probably is the cat, but I am wondering if anyone has had the problem and fix lately? Thanks. Quote Link to comment Share on other sites More sharing options...
camlex Posted June 1, 2009 Share Posted June 1, 2009 P420 is for Cat. Mine came around 275K. first mechnic put megnaflow two-three time . Code was comming back. Finally one good muffler shop used Orailly "walker" brand, today i am close to 355K. no problem Total cost was ~$240. Hope that helps. Quote Link to comment Share on other sites More sharing options...
RS1013 Posted June 4, 2009 Share Posted June 4, 2009 I also have a P420 code on my 97 Es300 with approx. $120,000 miles. My mechanic also told me to change the rear O2 sensor. However, the code comes and goes by itself after a few days. The O2 sensor behind the Cat was changed after a new exhaust system was replaced a year ago. Not sure if it is worth changing rear O2 sensor considering the previous threads. any ideas? Quote Link to comment Share on other sites More sharing options...
TomWoodLexus Posted June 7, 2009 Share Posted June 7, 2009 HA! I don't replace sensors off the bat. I can do a testing sequence to test the lag, crosscount, and voltage range of the sensors, then test for a bad cat. Than again, I am bragging. Get an EXPERIANCED Lexus tech to look at it! DON"T LET A N00B DO IT!!!! Quote Link to comment Share on other sites More sharing options...
George_Jetson Posted June 7, 2009 Share Posted June 7, 2009 HA! I don't replace sensors off the bat. I can do a testing sequence to test the lag, crosscount, and voltage range of the sensors, then test for a bad cat. Than again, I am bragging. Get an EXPERIANCED Lexus tech to look at it! DON"T LET A N00B DO IT!!!! Are you implying that you will not find any NOOB's at a dealership? like any other shop, some of the mechaincs are very experienced, some are not. If you get lucky you will get a good tech working on your car. The one thing you can count on at a dealership is THEIR HOURLY RATE IS HIGHER, and that is the only guarantee that you will have, as opposed to taking it to a independent garage. Quote Link to comment Share on other sites More sharing options...
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