Troubleshooting Trailer Lights When Connected to 2005 Jeep Grand Cherokee Limited

Question:

Same issue, replaced my trailer lights, everything, lights, sidelights, harness and plug with new, LED lights and nothing, no trailer lights work, checked all fuses and relays as mentioned in previous post, all good, ground down to bare metal and reground the trailer. Nothing, and the jeeps factory tow package plug work fine? I’m stumped, any thoughts? Thanks

asked by: Geoff H

Expert Reply:

The best way to troubleshoot trailer lights not wiring is to test each half of your towing rig separately. So for your 2005 Jeep Grand Cherokee you'll want to use a circuit tester like part # PTW2979 to ensure that each of the pins are sending power back to the various functions. Since it sounds like you already tested this your next step is to test the wiring on your trailer.

You can test the trailer wiring by either plugging it up to another vehicle or by taking a 12V battery, grounding the negative terminal, and then using the positive terminal to apply power to each of the pins on your trailer connector to ensure that each function is working properly.

If your trailer lights don't function properly then you'll want to inspect the wiring again. It might help to have someone else look at it as well (who has experience with wiring) as sometimes some fresh eyes can uncover something. If the trailer lights do function correctly then it might be that the LED lights aren't drawing enough power for the Jeep to recognize that a trailer is connected. I would try connecting a different trailer to your Jeep in this case just to make sure this is what is going on.

If you are still having issues with your lights working after all of that troubleshooting then the only other thing left is to take it to a shop so they can physically look at what is going on.

I have attached a troubleshooting article and some sample pictures of the vehicle connector for you to reference.

expert reply by: Jon G