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Discussion Starter · #1 ·
While towing with my small trailer I noticed as it was getting dark the running lights were not operating. While turn signal and brake lights were functioning normally, no matter what I did I could not get the running lights to operate. Tried both the 4-pin and 7-pin adapter and nothing. First thought it was my trailer so connected my Ascent up to my camper and again no running lights. To me this has all the earmarks of a blown fuse somewhere but I cannot figure out where. Fuse 28 in the cabin and fuse 8 in the engine compartment (for TAIL) are both fine. Is there another fuse somewhere with the Dealer-Installed tow kit I am missing?

Any suggestions/ideas appreaciated.

Thanks!
 

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My tail lights do not work on the 7 pin, but they work on the 4 pin. Bringing it to the dealer next week for them to have a look.
 

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Do you have the stalk set to on instead of auto? I am not sure that will make a difference but it may. I always tow with mine set to on to power a rearview camera.
 

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Do you have the stalk set to on instead of auto? I am not sure that will make a difference but it may. I always tow with mine set to on to power a rearview camera.
Mine is always set to auto. Hmmm...
 

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Maybe comparing apples to oranges, but I have a 2006 Dodge Ram diesel truck. I once hooked it up to a rather large horse trailer with lots of running lights. Shortly after turning on the running lights one evening, they all went out on the trailer. Long story short; the lights are switched through the ECU. The ECU senses the current on the light circuit. It's programmed to open the digital internal relay at 7amps. The lights drew 8 amps. I had to take to the dealer who reprogrammed the output not to trip until 10 amps.
The reason it's done this way instead of the old fashioned mechanical fuse is that it's much cheaper than adding an in-line fuse and the dealer gets to charge $100 for the reprogramming. I since changed the trailer to LED lamps so there is no chance of a trip unless there's an actual short. But even then, I'd have to return to the dealer if a hot wire ever did short. So I added a small fuse box for all the leads going to my 7 pin. Fuses are rated lower than programmed current trip point.
What a pain that was!
I don't know for sure, but perhaps this is how Subaru and other manufacturers are doing circuit protection for lighting.
 

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While towing with my small trailer I noticed as it was getting dark the running lights were not operating. While turn signal and brake lights were functioning normally, no matter what I did I could not get the running lights to operate. Tried both the 4-pin and 7-pin adapter and nothing. First thought it was my trailer so connected my Ascent up to my camper and again no running lights. To me this has all the earmarks of a blown fuse somewhere but I cannot figure out where. Fuse 28 in the cabin and fuse 8 in the engine compartment (for TAIL) are both fine. Is there another fuse somewhere with the Dealer-Installed tow kit I am missing?

Any suggestions/ideas appreaciated.

Thanks!
There is a trailer control module underneath the rear cargo tray on the driver side, check for voltage coming out of it. I had it replaced when about half the trailer lights wouldn't illuminate (both 4-pin and 7-pin). Replacement module has worked great.
 

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Have the same issue . Only half the running lights work . Only 10V coming out of then” module “ to the trailer . Going in is 13.8 ( alternator output ) . My power probe can illuminate all the lights on my intech trailer . Photos for clarity and help .
5368



harness with “ module “

5369

10.2 coming out of module to trailer 7pin

5370

alternator power going into module .
THE MODULE IS BAD

calling dealer tomorrow to schedule service. Hoping they can use my diagnostics to order the part versus giving me a loaner car .
 

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Discussion Starter · #8 · (Edited)
Have the same issue . Only half the running lights work . Only 10V coming out of then” module “ to the trailer . Going in is 13.8 ( alternator output ) . My power probe can illuminate all the lights on my intech trailer .
Sounds very similar to my issue, only for me it was 4v was being output. Good luck with your repair.
 

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Discussion Starter · #9 ·
Oh, just realized I never posted back to this question that indeed the module failed and was replaced by the dealer. My apologies for not providing the details on my resolution.
 

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Anybody see an issue with just jumping the box for the tail-light wire (brown) .? My dealer is backlogged and I can’t get an appointment for almost 2 weeks - even tho I can show them the issue and just need them to order the part.
 

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Anybody see an issue with just jumping the box for the tail-light wire (brown) .? My dealer is backlogged and I can’t get an appointment for almost 2 weeks - even tho I can show them the issue and just need them to order the part.
Looks to me like the copper is broken, which is a simple enough fix for someone adept at soldering.
 

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The copper is intact it’s just the spot I used a t pin on to check . The box isn’t properly directing the voltage . Seems to be relatively common from my research
 

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Just to update people on this . I used a jumper wire to skip the box and the lights worked . Towed a few times until my dealer got the new harness in stock . They then replaced under warranty and all is well .
 
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