common problem, bulletin released by gm, to follow
Some customers may comment that their windshield wipers stay on, even when they are turned off. Root cause appears to be a material inside the relay causing the relay to stick after it was turned off. Production fix was implemented in May, 2004. Service fix is to replace just the wiper motor cover kit (P/N 88958372) rather than the entire wiper assembly (arm, motor, links).
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.
(04 Chevrolet All Full Size Trucks and Utilities) and (04 GMC All Full Size Trucks and Utilities) and (04 Cadillac All Full Size Utilities)