Could be as simple as a bad bulb......

 

Yep, most of the time, it would burn out. Get one a little stronger than normal and it will handle the extra current.

 

Well like I said I started there by disconnecting all the taillight wiring. I suppose I’ll unplug the front parking lights and see if that helps. I’ll update tonight.

 

Disconnecting lights up front didn’t help. And now I’ve noticed when the blinker is going while the truck is running (parking light on or not) the fuel pump also is making noticeably more noise with the blinker as well in the same pulsating fashion.

 

Yea, you've got a ground going fubar somewhere.

Fuel pump uses Ground 113.