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Trailer Wiring Harness Installation on 2018 Jeep Grand Cherokee Sterling Edition  


I have a 2018 Jeep Grand Cherokee Sterling Addition, with the USCAR plug under bumper. I installed this part and took it to the dealer to activate. They looked at me like I just fell from Mars! Said it would be $149.00 just to figure it out! Then told me they would have to add fuses and everything to make it work at a substantial $. Does this sound right? I would think the fact that it has the USCAR plug would mean that it could be plug and play at some point? Please advise. Thank you.


Helpful Expert Reply:

The presence of a round U.S. Car connector could mean that there are some 'tow package' components installed on your 2018 Jeep Grand Cherokee Sterling Edition but there is no standard definition for what that term means.

One auto maker might refer to a dealer-installed hitch as a tow package, while another may define it as being a hitch + wiring + additional or upgraded cooling systems. Tow package can mean whatever the auto maker wants it to mean for their vehicles. What is fairly common is for any dealership to ask a premium price for this equipment.

Hopkins 7-way/4-Pole vehicle connector # HM40975 is a replacement part that will connect to the U.S. Car connector at your bumper. This in itself does not mean that the various circuits carried on that connector are active. Fuses and/or relays may still need to be installed to make that wiring active so it can transmit the various lighting, brake power and 12V power signals to a trailer.

You can test the socket # HM40975 with a circuit tester like # PTW2992 to see if any signals are there. Have a helper activate brake lights, turn signals and running lights and test the corresponding pins on the 7-way, one function at a time. Please refer to the linked photo to see which pins carry which functions; please refer to the linked video to see how the tester is used. You may need only install a fuse or two in the power distribution box, or you may find that the wiring is already active when you test it.

If you prefer to avoid spending more $ and time at the dealership, or if you just want to do it yourself, you can install 4-pole kit # 118727. This is intended for the Jeep without the 'tow package' but it will still work on ones with the tow package. This plugs in at your tail lights and requires you to run one wire up to the battery area. Installation is shown in the linked video and a help article is provided too. This kit will give you a working 4-pole no matter what the car does or does not have installed from the factory. This harness can then be upgraded to a 7-way setup using our kit # ETBC7.

Both of these parts, # 118727 and # ETBC7, will give you all the same functionality of a tow-package-equipped vehicle at a much lower price and without need to spend more time at the dealership.

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