P0420 Check Engine Light

[godzillatreat]

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.

[camlex]

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.

[RS1013]

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?

[TomWoodLexus]

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!!!!

[George_Jetson]

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.