Passenger upper taillight bulb does not flash.

[WyattTX]

Originally Posted by 95 S_Trucker

It’s a dual filament bulb. One filament for the running light, another for the turn signal/brake light. Most likely one of the filaments is burnt out. Replace the bulb and see what happens.

I forgot to mention I changed this bulb out the other day. It was failing at random times, and now it wont work at all. The wiring harness near the rear of the truck looks fine.

[WyattTX]

Tests confirm that I'm getting power to the socket in all 3 wires, and the bulb is just fine, but yet I'm still getting a failure reading, and the bulb isn't flashing. This doesn't make any sense.