The tail light wiring harness in the cargo area is not protected very well. As a result it may become damaged due to normal wear a tear. This damage can causing some or all of the rear lights to stop working.
Car Problem Reports
GMC Savana 3500 Tail Light Wiring in Cargo Area May be Damaged
GMC Savana 3500 Problem
Average Mileage: 67,916 mi (56,000 mi - 79,832 mi)