One problem related to windshield wiper/washer switch has been reported for the 2004 GMC Envoy. The most recently reported issues are listed below.
Turn signal failed and would freeze, or would activate the 4-way hazard lights. The dealership replaceed the relay switch. Approximately one-two months later windshield wipers came on without the switch being turned on after I had cleared mist from windshield ,and will not turn off, almost caused collision. The deaker said the internal module ruptured.