2008 GMC Envoy Owner's Manual - Page 144

Rear Window Wiper/Washer {CAUTION: In freezing weather, do not use your washer until the windshield is warmed. Otherwise the washer fluid can form ice on the windshield, blocking your vision. To turn the rear wiper on, turn the control to either 1, 2, or 3. For delayed wiping, turn the control to 1 or 2. For steady wiping, turn the control to 3. To turn the wiper off, turn the control to 0. To wash the rear window, press the washer symbol located in the center of the control. The rear window washer uses the fluid from the same reservoir as the windshield washer. However, the rear window washer runs out of fluid before the windshield washer. If you can wash your windshield but not your rear window, check the fluid level. The rear window/washer control is located to the right of the steering wheel on the instrument panel. 3-10