I have been told it is a knock sensor warning part of the emmission system - Now It appears that I have an electrical problem in the transmission. It either get stuck in overdrive or It will not go into overdrive at high speed. Only occurs when the car start after a cool off period. Turning the car off and re-start corrects the transmission problem - Any connection between the two issues
Warning Light on then off on 1999 Lexus RX300
Try changing fluid and filter. Worked for me. Stay away from dealerships, they told me my trans was blown and needed a rebuild which would cost a $10,000,000.00. I'm kidding of course. Its really hard to find a good mechanic these days. Most are nothing more than parts changers. Transmissions are tricky, So you need to find some who knows the tricks.Generally you won't find them at a dealership. a knock sensor can be the issue it puts your car into limp mode untill the problem is fixed. This can be a very expensive fix, considering the location of the sensors. there a two of themon top of the block. very hard to get to. Thus the labor costs. Buy two of them on line a d save yourself a ton of bucks compared to lexus. Have a local mechanic you trust to do the work.
Thanks but my problem was resolved - Yes the cost of O2 sensors is expensive. I do not use dealers - found a good mechanic. Thanks for the idea of buying Online. After market parts generally do not work on Lexus. Fixing the O2 sensors did fix the transmission problem so as you said it must have put the car in limp mode