Hi, I have an RX300, with around 130K. Still runs like a dream despite the Check Engine light coming on and off repeatedly for the last 4 months. I am getting around 18mpg city and haven't had any noticeable performance issues. I am not sure what exactly it is yet I am thinking it may be a faulty connection to B1S1 and the result of an open or shorted circuit. I don't have a wiring diagram and I am not very familiar with the wiring setup for that sensor.The error code that its displaying is the P0135, or as it is more commonly known, P1135.

This is my first post in the ClubLexus forums. Thanks for all of the help, this place is a lifesaver.

 

Welcome to the Club.

That is Bank 1 Sensor 1 A/F sensor behind the engine. Over time, that and the sensor in front of the engine can deteriorate and you will get the code popping up here and there. Same thing happened with me and eventually I replaced both sensors (I got codes for the front and back). At some point the code will come on permanently and the net effect is decreased gas mileage.