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2017–2022 Jeep Grand Cherokee WK2 Flat-4 Wiring Installation
Output: Flat-4 trailer-light connector
Connection method: Plug-in rear-lamp connections; no factory lamp wires cut
Power: Dedicated fused battery connection
Final connector location: Outside the vehicle at the hitch
Connector holder: Compact receiver-mounted flat-4 holder
Installation includes: Lamp access, converter and ground mounting, protected power routing, weather-resistant connections, secure reassembly, and full electrical testing
The WK2 wiring harness connects behind both taillights, crosses behind the bumper, and uses a powered converter with a fused lead to the battery. We finish the flat-4 outside at the hitch in a compact receiver-mounted holder rather than leaving the connector loose inside the cargo area.
1. Disconnecting the Battery and Removing the Taillights
The negative battery terminal is isolated first. Rear-hatch push fasteners are removed and each taillight is pulled straight rearward. Three factory connectors are separated at each lamp, with the locking tabs kept intact for secure reassembly.
2. Pulling the Driver-Side Branch into the Taillight Cavity
A pull wire is dropped between the vehicle body and bumper cover. From below, the driver-side wiring branch is attached and drawn upward into the lamp opening. Its matching connectors plug between the factory body harness and taillight without cutting or splicing the Jeep’s wiring.
3. Mounting the Converter Outside the Path of Road Spray
The powered converter is attached to a clean, flat surface behind the bumper where the rear tires cannot spray it directly and where it will not be pinched during lamp installation. Its ground terminal is secured to clean bare metal at an existing fastener or an approved grounding point.
4. Routing the Passenger-Side Branch Behind the Bumper
The passenger branch is carried across the back side of the bumper, secured at regular intervals, and pulled up into the passenger taillight cavity. It is connected between the factory harness and lamp, leaving enough controlled slack for lamp removal without allowing the wire to contact the exhaust.
5. Running the Fused Power Wire to the Battery
A dedicated 12-gauge power lead is routed forward along the chassis. It is kept away from heat, suspension movement, pinch points, and sharp metal. Grommets or sealant protect any sheet-metal crossing, and the fuse is installed only after the rear wiring, ground, and battery connection are complete.
6. Exterior Connector Mounting and Function Testing
The flat-4 is routed to the center of the receiver and retained in the compact hitch-mounted holder. We test running lights, brake lights, both turn signals, converter power, and ground integrity before the taillights, fasteners, and battery connection are restored.