One problem related to windshield wiper/washer switch has been reported for the 2003 GMC Envoy. The most recently reported issues are listed below.
While parked in my garage w/ engine off. I came around the corner & heard water running. My GMC 2003 Envoy's front windshield wipers were spraying spontaneously & wipers were running. Engine was making a loud screeching noise. Backed vehicle out of gargage & pulled out fuse. Spray stopped, but wipers still proceeded to go. Engine could have caught on fire! dealer replaced wiper motor stating it had been flooded w/ water. Previously to this event, the front wipers would go off & on even while switch was in the off position. Also, back wipers stopped working & had back wiper motor replaced too.