Funky problem here...
My 3 has lost it's left rear turn signal. the front signals are fine, but are blinking faster like the bulb is out. I replaced the bulb, but it didn't fix the issue. I've checked all related fuses under hood and in passenger kick plate area, so any suggestions would be appreciated as to further troubleshooting ideas.
Thanks!

 

I think there are individual fuses for the 4 corners of the car, could be that or the ground to that light... though I think both rear lights tie to the same point on the chassis (passenger side behind the rear seat), but they would be on seperate lugs to ground - possible that only one is broken. I'd check the fuses first though.

 

Thanks for the response. According to the manual, the rear blinker has a 7.5 amp dedicated fuse. I've checked it, and all the others, and they are perfect. The rear taillight and brake light work fine too, it's just the far left bulb that won't light. If it was a short, wouldn't that kill the front blinkers too? The front and side signals work though. I'm still stuck. Thanks in advance for any more ideas!

 

The rapid blinking is just the "light out" indicator. Basically if there's decreased resistance in the circuit (i.e. a light not lighting) it will make the other ones blink faster to let you know.

The side signals run off of the front signals so they'd continue working unless something was up with the front signal wiring.

If you've confirmed that the fuses are good and tried replacing the lamp itself I recommend getting out a multimeter and testing the power and ground at the socket. It's possible the socket is bad, the wiring going to the socket, or the ground/power connections to the wiring.

 

the 4 door uses two different locations to ground the rear lights, while the 5 door (hatch back) uses two locations but ties them together. so the ground could be that one wire that's corroded.
the source for turning them on is also a unique pin, so i'd verify the source voltage (right at the lamp) and see if it is pulsing on, and see if the ground side remains at ground when the turn signal is on.

 

I have had an issue with the RR running light in my car for some time now, especially using aftermarket bulbs and tails. I'm sure it's the socket that is funky, but have overcome it using some old-school methods.
The good news is that the sockets are separate from the harness. They unplug and can be replaced individually w/o cutting and soldering.

 

Thank you all. My issue has been resolved thanks to your expertise. The ground was exactly where described, and I was able to trace to the short in great time. Thanks again!