Jeep Wrangler (YJ) Wiring Harness – Wiring Harness for Want an affordable yet high-quality Jeep Wrangler (YJ) Wiring Harness? Shop now and enjoy our lowest price guarantee and access to the best brands in the industry! 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.