I installed new rear side marker LED's and Tail light LED's. All the lights light up except the passenger side inner tail light. I've tried moving all the lights around and flipping the LED's around in case it was a polarity issue but they all work except for whatever bulb is placed in the inner passenger side tail light. The only thing I've not done is install the hyperflash harness, but from what I understand that should only affect the flash rate when they are blinking, not the actual function of them working or not. Any ideas?

 

Since you've proven the LED is working, check for voltage at the socket. See if you might have loosened a wire from the socket. Also, be sure you have 3 wires connected to that socket. I have to think you need running light, brake light and the negative.

 

Does the incandescent bulb work in that socket?

 

yes it does. which is odd.

 

Since you said a previously tested good LED light didn't work in that socket and I think we can rule out a bad LED. And a known good LED will not work in either orientation in that socket.

I would test the socket with a DVM to make sure that you're getting the full battery voltage then. The only other thing I can think of would be to clean the contacts.