GM Service Manual Online
For 1990-2009 cars only

To wash the windshield, pull the windshield wiper/washer lever toward you while the ignition is turned to ON/RUN.

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.

When the lever is released, the washers stop, but the wipers continue to wipe for about two or three cycles and either stop or resume at the previous speed.