Here is what is how the truck connector is behaving.

1. Ground - correct
2. Brakes - incorrect, always 12V. Shouldn't this only be when brakes are applied?
3. Markers - incorrect. Does not show 12V when the truck lights are turned on. Shouldn't this be 12V with truck lights?
4. 12V Aux - correct
5. turn/brake - correct
6. turn/brake - correct

Could a relay or fuse on the truck be causing these symptoms?