GM Service Manual Online
For 1990-2009 cars only

Press the button at the end of the windshield wiper lever until the washers begin.

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 button is released, the washers stop, but the wipers continue to wipe about three times or resume the previous speed.