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Trailer wiring

JimAC

By JimAC
in Ask A GM Technician

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JimAC Enthusiast

JimAC

Posted
Posted

I have a 2004 silverado 2500 LT fwd crew cab and it has the factory trailer package. All the lights on the truck work properly and when a trailer is plugged in the turn ,hazard,and lights all work properly. Only the left brake light will light on two different trailers even though the right turn signal works fine.

Something did happen to the truck once that blew two fuses for the trailer plug

 

Any thoughts ?

Thanks, Jim

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted
Only the left brake light will light on two different trailers even though the right turn signal works fine.

 

This part doesn't make sense. What does the left brake light have to do with the right turn signal?

 

The turn/brake power is on the same wire. If the turn signal works on a side, the brake light on that side should also work. The trailer right/left stop/turn is individually fused.

JimAC Enthusiast

JimAC

Posted
  • Author
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Only the left brake light will light on two different trailers even though the right turn signal works fine.

 

This part doesn't make sense. What does the left brake light have to do with the right turn signal?

 

The turn/brake power is on the same wire. If the turn signal works on a side, the brake light on that side should also work. The trailer right/left stop/turn is individually fused.

 

 

 

 

Could there be an open connection between the truck brake wire and the right trailer brake /turn light ? When I test the plug with a plug in led tester only one led lights when brake it applied

the lights dont have anything to do with one another I just stated that all light functions work properly except the right brake light does not come on when you apply the brake on two different trailers . The right turn works but not the brake

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted

The turn/stop functions for the trailer come from the flasher module in the IP fuse box.

 

If the turn signal works, then the wiring is good all the way from the trailer connector to the flasher. It's the same wire and protected by the same fuse, so if the turn signal works but not the brake light, I can't see where it would be anything but the flasher.

JimAC Enthusiast

JimAC

Posted
  • Author
Posted
The turn/stop functions for the trailer come from the flasher module in the IP fuse box.

 

If the turn signal works, then the wiring is good all the way from the trailer connector to the flasher.  It's the same wire and protected by the same fuse, so if the turn signal works but not the brake light, I can't see where it would be anything but the flasher.

 

 

 

I can see that the flasher module is under a fuse block but I also see that there is a trailer 6 way relay in the ip relay block .are they different ?

And if it is the flasher module how do you get to it

JimAC Enthusiast

JimAC

Posted
  • Author
Posted

Thank you GM-Tech , you were right . I replaced the flasher module and everything is fine now. $46.00 and 10 min to get it working.

I was able to replace it myself

 

The turn/stop functions for the trailer come from the flasher module in the IP fuse box.

 

If the turn signal works, then the wiring is good all the way from the trailer connector to the flasher.  It's the same wire and protected by the same fuse, so if the turn signal works but not the brake light, I can't see where it would be anything but the flasher.

 

 

 

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