Circuit/System Description
WARNING: This page is about a different car, the 2016 GMC Acadia, 2016 Chevrolet Traverse, and 2016 Buick Enclave. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) controls the washer motor based on an input from the windshield washer switch, a part of the multifunction switch. The BCM monitors the washer switch through the windshield washer pump control circuit. When the WASH switch is closed, accessory voltage is supplied to the BCM which will command the windshield washer fluid pump and the low speed wipers On.