One problem related to windshield wiper/washer has been reported for the 2004 GMC Envoy. The most recently reported issues are listed below.
2004 GMC Envoy wiper module assembly failure. Intermittent failure of windshield wipers. Failed to turn off when turned to the off position. Chp helped me find and pull the fuse out to turn them off. After vehicle sits for a few days, wipers turn off. $435 for dealer replacement. Vehicle was purchased on 03/05/2004, but I neglected to get it to the dealer until 03/16/2004. GMC says sorry, its out of warranty. 31k on vehicle. Dealer will have replacement part in, 3 days from today.