2003 ex OEM trailer connection issue

[kapem23]

Ok here is my issue- 2003 excursion when plugged in to my travel trailer the left blinker and left brake light do not work on the trailer but they work on the ex. Here is what i have done.
I tested the trailer side by hooking up my dad's truck and every thing worked like it is supposed to. I then got my multimeter and tested the truck side on the corresponding pins for the blinker on both sides. With the right blinker on; the multimeter reads 12.0 v when it blinks on and then zero when it blinks off ( which is correct to my knowledge).
The left blinker reads 12.0 v when it blinks on and 10.3v when it blinks off. The problem is definetly the pin for the left side of the trailer. At first i thought it might be a ground issue but both the right and left side share the same ground and the right side reads like it should but the left side does not. Any suggestions or tips would be greatly appreciated.