Circuit/System Description
WARNING: This page is about a different car, the 2020 Buick Regal TourX, 2020 Buick Regal, 2019 Buick Regal TourX, and 2019 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
The rear windshield washer pump is controlled by the body control module (BCM) via a printed circuit board (PCB) relay. The BCM monitors the rear windshield wiper/washer switch signal circuit and when rear washer activation is requested, the BCM applies voltage through the rear window washer pump relay control circuit. With the relay energized, fused battery voltage is applied through the switch contacts of the relay and the windshield washer pump control circuit to activate the windshield washer pump.