Passenger upper taillight bulb does not flash.
 

On my 2015 K2500, when I turn on the right turn signal I get the warning on the dash saying there is a failure. The bulb still lights up as a running light, and the driver side works fine. Is there something knocked loose under the truck, or am I in for some sort of electronic headache? Thanks.

Re: Passenger upper taillight bulb does not flash.
 

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.

Re: Passenger upper taillight bulb does not flash.
 

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.

Re: Passenger upper taillight bulb does not flash.
 

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.

Re: Passenger upper taillight bulb does not flash.
 

1 wire should have power with the running lights. 1 wire should have power with the brake/signal lights. 1 wire should be ground.

The running light wouldn’t work if ground wasn’t present.

Is it a wedge 7443 bulb?

Re: Passenger upper taillight bulb does not flash.
 

I think I've figured it out. It appears the contact that makes the turn signal/flasher filament work in the socket got mishapen somehow. I am now on the hunt for a new socket. All I can find on the internet is license plate bulb sockets, and LED conversion sockets. I'm hoping I can find 2014-2019 wreck, I can cut a socket out of and splice into my harness. I'd rather not have to pay GM for a new rear light harnesses, when the rest of mine is fine. Thanks for the advice everyone.