How do you unplug the sensor?
I'm assuming that, like on most Toyota vehicles, one has to partially remove the fender liner inside the wheel well to access the electrical parts for the windshield/headlight washer reservoir. Here is an illustration of the components: http://www.toyodiy.com/parts/p_U_1999_LEXU...EAGKA_8503.html
Thanks! I'll probably get the dealer to replace it.