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Trailer Running Lights Not Functioning with a 2007 Dodge Ram Pickup


I have a 2007 Dodge 2500 with the 5.9 diesel. I just purchased a trailer and discovered the running lights on the trailer weren’t functioning. The brake and turn signal lights were however functioning. Any guidance on troubleshooting, correcting this problem?


Expert Reply:

There are a couple of things we can do to troubleshoot malfunctioning wiring on your 2007 Dodge Ram Pickup. I've linked to an article about troubleshooting your wiring issues below.

If the turn and brake lights are working but the running lights are not, then the first and easiest thing to do is to check your fuses. The 2007 Ram has an integrated power module that houses its fuses. It's right next to the battery. Check cavity number 15 (it's a 20 amp yellow fuse) for the trailer running lights. If that fuse is blown, you need to replace it.

If that is okay, then another easy thing to do is clean the vehicle and trailer grounding locations (typically a white wire). If there is any corrosion or paint getting in the way of the contact area, then there won't be sufficient power going through the system, which can cause malfunctioning. Be sure to check for a clean connection area (avoiding paint or rusted areas) for your ground. Move them to better spots if need be.

If that doesn't solve the problem, then the next thing to do is test the wiring harness with a circuit tester like the Hook Probe, part # PTW2993. I've linked to a video review of this tester that demonstrates how to do this. Depending on whether or not your Pickup has a factory-installed 7-way or an aftermarket 4-way pole, you'll need to determine which wire to test. Generally (though not always), a 4-pole has a brown wire for its running lights.

If everything checks out up to this point and the running lights are still not working, then the problem is with the trailer wiring. To find the exact point, you may need to trace the wires on the trailer side and look for any places where the ground wire is exposed and making contact with the trailer frame, which would "ground the wire out," causing it to malfunction. If you find any splits or frays on one of the wires, then you will need to replace that wire.

expert reply by:
Kef G

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