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Troubleshooting 7-Way Install on 2015 Jeep Grand Cherokee that Doesnt Function After Install


I have a 2015 Jeep Grand Cherokee Laredo with a factory installed trailor wiring wire which I plugged into the HM40975 part but did not work. Does the Jeeps headlight switch need to be on a certain setting or is there any other step I needed to perform to get the system to work properly? I tested the trailor on another vehicle and the lights worked with it. So either it is my cars wiring or the HM40975 unit itself. Thanks


Expert Reply:

It could be as simple as the connector not being pressed all the way together, but most likely that is not the problem so what you will need to do is test the pins of the connector that is on your vehicle that you plugged the part # HM40975 into for voltage when the taillight functions of your vehicle are applied like in the video I attached. You will need a circuit tester like part # PTW2993.

If there is voltage on those pins then the problem is either that the # HM40975 isn't connecting properly to the harness or the # HM40975 is bad.

If there is no voltage there then the problem is most likely missing trailer wiring fuses or relays under the hood of your vehicle.

expert reply by:
Jameson C

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