High Speed Operation
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
With the wiper switch in the high position, the body control module (BCM) receives two signals, one from the windshield wiper switch low signal circuit and one from the windshield wiper switch high signal circuit. When the BCM detects these two signals, the BCM then applies voltage to the wiper high speed relay control circuit. This energizes the WIPER relay and allows voltage to be applied from the switched contacts of the WIPER relay to the high control circuit of the wiper motor.