Circuit/System Description
WARNING: This page is about a different car, the 2010 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) controls the windshield washer fluid pump based on an input from the wiper/washer switch. The BCM monitors the washer switch through the wiper/washer switch signal circuit. When the wash switch is closed, ground is supplied to the windshield washer switch signal circuit. When this is the case, the BCM will command the windshield washer fluid pump and the low speed wipers on.