Q&A

 Master

Check the 25 amp wiper fuse #14 and the 10 amp Wiper Switch fuse if you haven't. There are two wiper relays, too. There's Wiper 1 Relay 39 and Wiper 2 relay 40 that you need to check. This is not so easy to diagnose, you may need to find an auto electric shop or a GM specialist for help. They'll have electrical schematics and the knowledge to make it easy.
Here's a directory link for you:
https://repairpal.com/directory?address=48206&car_brand_n...
If you want to find out more and try it yourself, here are two sources for you:
For AllData:
http://bit.ly/AllData_Repair_Manuals_Online
Here's the one for Mitchell as well:
http://bit.ly/mitchell_repair_manuals_online

 Technician

Give us a call and schedule an appointmnet. We have the diagrams and the trained techs to repair this