98 Silverado. I am having odd issues with my right rear tail light. The turn signal won't work and the brake light doesn't work when pressed. The tail light does turn on when I turn on my lights for driving at night. I have replaced all lights within the tail light and replaced the turn signal relay under the dash. Any suggestions on what the cause might be or places to start troubleshooting at? Thanks.

 

Check the circuit board in the tail light assembly. They get corroded and will cause issues like your describing. There are replacement boards available.