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Discussion Starter · #1 ·
When I hook up my trailer I don't have any running lights on my trailer. I do have brake and turn signal lights, and my trailer uses the 7 pin. The only functions I use for the 7 pin are for lights, the previous owner ordered it with a 7 pin because his vehicle didn't have a 4 pin hook up, it is a sealed harness and I don't want to cut it. I measured the voltage on both the 7 pin and the 4 pin hook up for the running lights at only 4 volts from the Ascent. I can only find 1 fuse labeled as trailer. Are there secondary fuses for each function of the lights ( stop, turn, running)? The hitch was factory installed. It's not the lights on the trailer, I used a 12 volt battery from my kids power wheel and checked the lights. They all work as intended.

Thanks for any help anyone can provide. With the stay at home orders, I don't want to bother the dealer, but will have it checked/replaced under the factory 3/36k if needed.
 

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When I hook up my trailer I don't have any running lights on my trailer. I do have brake and turn signal lights, and my trailer uses the 7 pin. The only functions I use for the 7 pin are for lights, the previous owner ordered it with a 7 pin because his vehicle didn't have a 4 pin hook up, it is a sealed harness and I don't want to cut it. I measured the voltage on both the 7 pin and the 4 pin hook up for the running lights at only 4 volts from the Ascent. I can only find 1 fuse labeled as trailer. Are there secondary fuses for each function of the lights ( stop, turn, running)? The hitch was factory installed. It's not the lights on the trailer, I used a 12 volt battery from my kids power wheel and checked the lights. They all work as intended.

Thanks for any help anyone can provide. With the stay at home orders, I don't want to bother the dealer, but will have it checked/replaced under the factory 3/36k if needed.
Tail running lights should be on the brown wire at pin 3, use a multimeter or test light to see if you have voltage on pin 3 on the car plug. Here's a diagram to help with the pinouts. A bad ground is probably the most common reason lights fail. Yes, some of the lights will work and others won't.
 

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Discussion Starter · #3 ·
Tail running lights should be on the brown wire at pin 3, use a multimeter or test light to see if you have voltage on pin 3 on the car plug. Here's a diagram to help with the pinouts. A bad ground is probably the most common reason lights fail. Yes, some of the lights will work and others won't.
Thank you for the suggestion. I measured the voltage on both the 7 pin, and the 4 pin for the running lights, and only get 3.66 volts.
 

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Thank you for the suggestion. I measured the voltage on both the 7 pin, and the 4 pin for the running lights, and only get 3.66 volts.
I'd have that checked out.
 

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Ok, the pinout should be pin 3 for running/tail lights, Pin 4 is for charging a battery or providing voltage for some other device in a trailer. Pin 7 is for backup lights. What do you see on pin 5(left signal) and 6(right) make sure car is running.4 way flasher on. Low voltage is an indicator of a bad ground. I don't know if you were using pin 1 for your ground source, try using another ground contact under the car somewhere, somewhere on the frame or hitch mount bolts. If voltage is good then, pretty much confirms the factory ground is bad.
 

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Discussion Starter · #6 ·
Ok, the pinout should be pin 3 for running/tail lights, Pin 4 is for charging a battery or providing voltage for some other device in a trailer. Pin 7 is for backup lights. What do you see on pin 5(left signal) and 6(right) make sure car is running.4 way flasher on. Low voltage is an indicator of a bad ground. I don't know if you were using pin 1 for your ground source, try using another ground contact under the car somewhere, somewhere on the frame or hitch mount bolts. If voltage is good then, pretty much confirms the factory ground is bad.
OK, need to clarify. On the running light (pin 3) on the 7 way round I am getting 3.66 volts. All other pins test as should, brakes, reverse, left turn, right turn, battery are all 12 volts.

On the 4 way flat, I am also getting 3.66v for the running lights, brake and turn signals are getting 12v.
 

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I'd watch this video on installing the hitch, at 13:00 he is installing the wiring harness in back compartment and you can see how he takes that apart. Underneath he plugs the cable from the trailer connector into a module and then the module into a connector in the car. I guess I would check and make sure the connections are good at those points. PIns have been known to back out of connectors, when plugged together and cause poor connections. I keep getting calls from my dealer to bring my car in if I think it needs service so they are trying to keep their employees busy. Next step would be to take it in.
 

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OK, need to clarify. On the running light (pin 3) on the 7 way round I am getting 3.66 volts. All other pins test as should, brakes, reverse, left turn, right turn, battery are all 12 volts.

On the 4 way flat, I am also getting 3.66v for the running lights, brake and turn signals are getting 12v.
There is something definitely not right with the wiring on the truck if you are only getting 3.66v from pin 3. You should be getting 12v for running lights at pin 3.
 

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Discussion Starter · #9 ·
I made an appointment with the dealer to have the issue looked at. Couldn't get in until April 19th. Figured since it is still under factory warranty, I will have them figure out the issue. No sense in me messing with it. Of course, when I called and talked to them about it. They were positive it was an issue with the wiring on my trailer, and not the vehicle itself. I explained to them that I tested the voltage for the running lights from the vehicle, and it is only 3.66v. Certainly an issue with the vehicle.
 

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I had problems with only some of the trailer lights working...it was the trailer control module (underneath rear cargo area). Dealer should be sure to check voltage at the controller. Super easy to replace if that is the problem. I haven't had an issue since.
 

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Nope
 
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