RepairPal Certified shops can diagnose and repair your 2003 GMC Savana 1500. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
You could have an issue with the heated seat element in question itself. You will have to check the element for resistance. Troubleshooting the system per the shop manual instructions is the only real way to find out what's going on.