One problem related to automatic transmission has been reported for the 2002 Lexus GS300. The most recently reported issues are listed below.
Sudden acceleration after turning a corner. I slowed down to turn a corner to approximately 10-15 mph and after negotiating the turn accelerated moderately to about 20-25 mph. At that instant the motor started to race. The car accelerated rapidly in a few seconds to approximately 35-40 mph. I applied the brakes and got the car to slow down to 20-25 mph. When the brake was released the engine started to race again at an accelerating rate. I the decided to abort the acceleration and stop the car this time by throwing the shift into "park. " when I attempted to do that the automatic shift went only as far as neutral. I quickly realized that being in neutral was ok and applied the brake and pulled over to the side of the road and called the dealer. The dealer picked up the car. The dealer told me it was/must have been caused by the floormat sliding under the accelerator. I did not believe that because the floormat if it got under the accelerator pedal would have caused a constant acceleration. In both cases the car accelerated at an accelerating rate. I asked the dealer to call Lexus to see what they said about this. Eventually when I spoke to them they told me Lexus confirmed their diagnosis. They knew of no other cause for the problem.