Troubleshooting No Running Light Trailer Wiring Circuit of 2012 Ram

Updated 07/27/2021 | Published 07/25/2021

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Question:

When I hook up my fifth wheel I have turn and brake lights on the trailer, no running lights. I have a second truck with a factory 7 pin plug and hooked the trailer to that and everything works as it should. So the trailer is not the problem. I even have a 24x24inch Test board that I rigged up with all of the lights a trailer would have just so its easier to check the lighting circuits. That doesnt work on my towing truck but does on my other. With that, I have totally ruled out the trailer as the problem. Now, on my towing truck, I have checked the fuses and they are all good. I unplugged the factory wiring at the rear plug, cleaned and re-applied die-electric grease. I checked the wire harness as best as I could without unwrapping the entire length of it crew cab and 8 foot bed, lots of length and found no wear spots or tight bends where damage might occur. All of this and still no running lights on my trailer. Can I direct wire the plug and bypass the factory wiring? Will that damage anything in the truck?

asked by: Kevin

Expert Reply:

You can run your trailer running lights off of your truck's running light circuit if you wanted to but I'd only really recommend that if your trailer has LED taillights on it. The draw might be too much if they are incandescent.

Your generation of truck also has a TIPM for the trailer wiring circuit protection which can be only reset from a dealer. You could also use the # 119178KIT as a way to bypass it though and you'd not ever have to worry about what you are experiencing now.

expert reply by: Jameson C