What is this wire found under the trunk carpet beside the spare tire, coming out of the white square appears to be cut. What is it for?
That doesn’t look like factory-installed wiring, and it would be unusual to have a single wire on its own. Nothing is shown at that location in the Electrical Wiring Routing pages of the Electrical Wiring Diagram (more info). Perhaps it was a chassis ground connection for aftermarket equipment that has been removed.
