2003 Chevrolet Express codep1626

Thi smay be a body control module problem or a wiring issue like a wire rubbed through or broken inside of it. It may also be a connection problem at body module and or module lost ground. They key doesn't have much to do with it as that system isn' t on that vehicle It has no diode. This is something a pro should check out as it may require anew body module which would have to be programmed to the truck