Washer Signal Circuit: Description
WARNING: This page is about a different car, the 2007 Lexus ES 350. However, it is still accessible from the selected car via links, so may be relevant.
The distance control ECU detects washer operation. The cruise control will be cancelled by the distance control ECU if the windshield wipers operate in HI mode for 5 seconds or more. By detecting washer operation, the distance control ECU allows the cruise control to continue even when the windshield wipers operate in HI mode.