Look back a few months in this Forum, this is a common problem and GM had a recall but the fix is easy, read the threads about wiper problems and you'll see. All you do is take out the circuit board from the wiper motor (on firewall driver side) and put a new one in or repair it by re-soldering the connections where it plugs in, be careful not to crack the board and I also cleaned off the contacts that rotate around with the motor. Good Luck!
