[JMD]

Installed the replacement tail lights from LMC, same problem. Doesn't look like the tail lights are the problem.

I think I've completely ruled out a bad ground at this point. I cut the "socket" end of the tail lights off and hardwired it. I ran a jumper wire straight from the negative lead to the negative battery post, and crimped the running and brake light leads to the proper wires coming straight out of the fuse box. No change.

I installed an electronic flasher with a ground wire. No change.

The tail lights are manufactured by United Pacific and feature "sequential flash" and "Brake attention", which apparently means the lights will flicker one time when the brakes are applied. The flicker feature doesn't appear to be working, maybe that has something to do with the problem?

The back of the package says that a United Pacific LED turn signal flasher item #90652 is required (funny how LMC doesn't mention that in their catalog) I looked up that part number on Summit, and it appears to be the same as the flasher I just bought, just a different brand. Maybe there's something special about their flasher?

I'm going to call United Pacific tomorrow, hopefully they can steer me in the right direction.