I just got off the phone with my dad, he said he is having somewhat similar problems with his car. It's not an SC or anything, but his mechanic said his problems are coming from the amount of ethanol that is being put in the gas now. His mechanic took his fuel pump off and said it was full of alcohol. He cleaned it out and gave him some specialty ethanol treatment stuff. I plan on doing the same thing to my car. Maybe an Alcohol buildup is what's triggering the knock sensor, and putting the car into safe mode.

I am no Lexus master mechanic (although I feel like one after all this) so I dont even know if there really is such a thing as a "safe mode". But i have talked to a couple Lexus mechanics and they say that when the knock sensor is triggered, the car with go into safe mode, witch retards the timing a little, and richens the air fuel ratio, to keep the motor from blowing up. If this is true, I would assume the richer exhaust gases is whats causing the o2 codes to go off.

We seem to have tried everything else so I will give this a shot and let you know if it makes any difference at all.