Did a couple searches and none of the fixes worked.
My drivers side tail light doesnt turn on when the headlights are turned on but works when the brake os applied. The passenger side is working fine.

I have bent the contacts back out, replaced fuses, replaced bulb, and now whats left ?

Thabk you

 

Has to be the wiring some where then right? I'm not to handy with electrical but there should be a way of checking continuity with a multi meter.

Maybe someone else will chime in.

 

they are a dual filament bulb, one is for the parking / running lights, the other is for brake lights. I wonder if you have a ground bad on that side

 

Ive read about the ground issue but I havent seen anything to say where the ground actually is. My current plan is to check the contacts for ground and power and possibly cut the harness out and splice another one in.

 

have you tried turning on the running lights, and then with a glove on, wiggling the light bulb in the socket to see if it comes on? If so, the issue could be with the socket itself

 

Replaced rhe harness and everything now works. The chip inside must have crapped out

 

good to know!

 

Hello I ran across your post. It's been a few years, but by any chance were you able to solve this issue?

 

Read post #6.

However, you have a 99 GRAND Cherokee according to your title, which is a WJ. This is the XJ forum. What works for an XJ might not work for a WJ. You could have a wiring issue, a bad ground, or something else entirely.

Here is the WJ forum > https://www.cherokeeforum.com/f5/