Circuit/System Description

The body control module (BCM) controls the rear washer based on an input from the rear wiper switch, which is part of the windshield wiper/washer switch. The BCM monitors the windshield wiper/washer switch through two separate signal circuits and a low reference circuit. The rear wiper switch uses a resistor ladder to determine low speed, intermittent, and rear washer operation. The BCM monitors applies and monitors voltage on the rear wiper switch signal circuit. When the rear wiper switch is placed in the low speed, intermittent, or rear washer position, the voltage is pulled down through a different resistor in the resistor ladder, reducing the voltage seen at the BCM. The BCM will respond by commanding the specific rear wiper function.

The windshield washer uses a single windshield washer pump to provide fluid for both the front and rear washers. Changing the polarity of the motor will cause it to spin in opposite directions, feeding fluid to the front or rear. When rear washers are requested, the BCM applies voltage to the rear window washer pump relay control circuit. This causes the contacts in the rear washer pump relay to close and supplies voltage to the windshield washer pump. Ground for the windshield washer pump is provided through the windshield washer pump relay, which is switched to ground in it's at-rest state.