New to LOC, however found much in the way of assistant and enjoyment, thanks to all how take part.
Our 2000 RX300 has the same issue with O2 sensors (Air/Fuel Ratio Sensor). Where when they go bad your engine loses much in the way of performance, and fuel efficiency. Lexus diagnosed the problem as system lean bank 1, in addition the codes also read cylinders 2, 4, and 6 misfiring. The on board system computer attempted to correct this. However when the misfiring occurs often enough the system computer can not adequately adjust enough for the problem.
We did replace all 3 O2 sensors, 2 in front of the CAT, and 1 aft the CAT. To my surprise only after 115 miles the check engine light comes on. I then read the codes again, P0171, P0441, P0444, P0446, "Bank 1 Lean" and "Cylinders 1, 3, and 5 misfiring" I understand that some code readers run generic system test, and they vary. At this point I contacted Lexus Customer Service and asked "What is going on here, please help." Maintaining a very polite and respectful manner. They researched the vehicle maintenance history and found that just prior to my purchase, less than a year the O2 sensors were also replaced by the previous owner. Wow, did I blow my top. How is it possible that my local Lexus tech would recommend a solution, when that same solution has been only recently done without actually being the correct solution. Well needless to say, at this point Lexus Customer Service said that they would follow up with the local dealer and seek applying a Goodwill warranty. So here I sit waiting for the call. I will keep you folks updated as this issue unfolds.
