Proximity sensors generated an alert that parking assistance sensors needed cleaning during moderate rain cleaning the sensors did not resolve the issue. Stopped at dealer to have it checked and was advised that the sensor do that in inclement weather and I would need to learn to live with it. If it was just the parking sensors it would not be as significant but I did determine the front accident assistance did not function as it should have - as I approached a vehicle in front of me with cruise control the speed reduction that was supposed to occur did not happen. Had I not been checking to see what would happen if the proximity sensors were malfunctioning it could have resulted in an accident. I did not attempt any other actions which rely on proximity sensors to function as I did not want to cause or be involved in an accident. I was driving at the time and I expect that although the alert specifically mentioned parking sensors, the fact that the car did not slow as Toyota has indicated it should leads be to believe that any and all "driver assistance technologies" may fail when that alert occurs resulting in potential accidents and injuries the vsc off indicator was flashing at the time.

- Fincastle, VA, USA