GMC Repair: 1999 GMC Sierra trailer plug, light flicker, gmc sierra

Question
We have a factory installed trailer plug. When we hooked up our trailer it worked good.  After a year just the right side works.  Checked fused and replaced the one on the left side.  Now it works but when it works their is a trickle of light on the other side. We think it is a short.  Could you please give advise on how to find this short.   Thank you for any advice.  Cathy

Answer
Hi
I would almost be CERTIAN it is NOT a short but a faulty ground.
If you use a test light and test the plug left circuit and ground.
If the light "flicker" like you describe it is a problem with the truck's ground circuit.
It it DOES NOT flicker, it is the trailer wiring, which I would HIGHLY suspect, as the SAME ground circuit is used by the plug.
I Hope this helps
Pawl