This morning, when I was driving my car from my apartment building, I noticed that the left turn signal was flashing much faster than before.
Then I noticed that the left rear turn signal was not working.
So I bought a new PY21W bulb in the store, replaced it in the left rear light, but unfortunately it did not help...
Since replacing the bulb did not help, I would like to ask for advice on what is the possible cause?



Here is a video showing how to replace this bulb:

 

It turned out that the entire left rear light was not working, so following the thread to the ball it turned out that the black plug powering the entire left rear light had come loose.
I inserted it into the black socket and everything works now.

 

Thanks for sharing the solution.

 

I'm happy that you have resolved the issue!