12 Pin Harness | etrailer T-One connector plugs directly into existing wiring - no cutting, splicing or tapping required. This harness plugs into the 12-pin plug that is located behind the passenger's-side kick panel in your cab. Once installation is complete, the 4-way flat connector will be stowed beneath your vehicle, near 12 pin wiring harness | eBay Find great deals on eBay for 12 pin wiring harness. Shop with confidence. Skip to main content. eBay Logo: 6/12/24V Trailer Wiring Harness Extension 4 Pin Plug Flat Wire Connector Adapter. Brand New · Unbranded. KENWOOD 12 Pin Wiring Harness for Car Stereo with 12 Pin Male Socket at Back NEW See more like this.