Thanks for reaching out, Erik!
The T-One Vehicle Wiring Harness # 118791 will potentially work, but we've received feedback that the connectors don't always match up with the tail lights so I recommend using the Curt Universal Wiring Harness # C59236 instead.
The Curt wiring will need to be spliced into your vehicle wiring so you will need to test and figure out what wires carry which functions. If this isn't something you're comfortable doing I've gone ahead and linked out installer... view full answer...
Thanks for reaching out, James!
The T-One Vehicle Wiring Harness # 118572 you're looking at is for the Sedan version of a 2012 Volkswagen Jetta. Since you have a Wagon you'll need universal wiring like the Curt Powered Tail Light Converter w/ 4-Way Flat Trailer Connector # C59496 which splices into your factory wiring as opposed to teeing in behind the tail lights. view full answer...