Jeep Chassis Wire Harness - Engine & Transmission Wiring The purpose of a Jeep YJ wiring harness is to deliver electrical and other information to places your rig needs it. Many of the Jeep's systems have their own wiring harnesses. For example, your rig has a Jeep transmission wiring harness and an engine wire harness assembly. Unfortunately, over time, wiring harnesses can wear out. Meyer Plow Main Harness Wiring Pin Outs - Meyer Snow Plow Meyer Plow Main Harness Wiring Pin Outs. These are the "1 Piece Plug" and Universal Wiring Harnesses. The 1 Piece Plug made its debut with the MDII Mount. The MDII made it necessary to unplug EACH plow light, the 3 individual Coil wires, and the Motor Harness to remove the complete plow assembly. Meyer came out with the 1 Piece Plug.