BMW X5 Trailer Wiring | etrailer Trailer Wiring Harness Installation - 2012 BMW X5. Today on our 2012 BMW X5, we're going to take a look at and show you how to install the Tow Ready Upgraded Heavy-Duty Modulite Circuit-Protected Vehicle Wiring Harness with Install Kit. The part number is 119190KIT. Here's what the alternative mounting solution looks like. BMW X5 Hitch Wiring | Harnesses, Adapters, Connectors When you tow with your BMW X5, you’ll have no problem making the electrical connection to any trailer with our selection of harnesses, adapters and connectors.