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Trailer Light Issue

Logan Lanfear
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Logan Lanfear Enthusiast

Logan Lanfear

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Hey guys,

My 2000 GMC Sierra has had an issue since I purchased it.  While towing, the left side trailer light does not work. I had previously chocked this up to a trailer with a bad light but I recently replaced the lights on a new to me utility trailer.  This "new" trailer had the same issue with no left side marker light, brake light or blinker. I have checked the fuses as well as changing the bulbs around on the trailer. I have confirmed with another vehicle that the lights work correctly on the trailer.  Yet when I plug my truck in, I only have the right side lights. The right side is bright and working well. My truck has the factory tow package with the 7 pin round style plug. I have taken the plug apart and found no corrosion. Im not sure if a wire got crossed somewhere or if there is a light issue on the truck. Any help or spots to check would be appreciated. I will double check my fuses and make sure that they are all functional. 

diyer2 Senior Enthusiast

diyer2

Posted
Posted

Look under the rear bumper. Check wiring harness.

Have you checked the plug with a test light? 

:)

Logan Lanfear Enthusiast

Logan Lanfear

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Posted

No visible problems with the harness or the plug.  Also no power at the plug tested with multiple trailers as well as a multimeter.  Also update: I have no brake lights at all just right side blinker and running light. 

rjgti Enthusiast

rjgti

Posted
Posted

i think that there is a junction box above your spare tire for the rear harness, have a look there

Logan Lanfear Enthusiast

Logan Lanfear

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Posted (edited)

Checked the harness, no problems there either.  I'm not the first person to be in here searching for the problem. Honestly, i've been looking for a reason to upgrade and this might be it.  Either that or im tapping into the taillight harness just to get me by. 

Edit:

Got it figured out, turned out to be a burnt wire in the trailer harness.  Im guessing it was due to a bad ground.  I cleaned the grounds and fixed the wires.  Hopefully it doesnt repeat. 

Edited by Logan Lanfear

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