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. Engines & Components for Jeep TJ - eBay Good Used 1999 Jeep Wrangler TJ Dash Wiring Harness. This connects to the heater and air conditioning switches. It has been tested and is in good working condition. Will fit TJ model year 1999. This harness will work on a Jeep Wrangler with either a 4 cylinder or a 6 cylinder and either an automatic transmission or a manual transmission.