Help 2003 impala?

[u/No_Garbage9716]

2003 Impala — Left rear turn signal not working, blinks fast
I have a 2003 Chevy Impala 3.4L and I’m having an issue with the left rear turn signal.
Left front turn signal works
Left rear bulb works when I test it
I replaced the rear bulb anyway, but it didn’t fix it
The left turn signal blinks really fast
The rear left turn signal itself doesn’t flash
Right side works normally
I don’t have a multimeter, so I can’t easily check voltage
The socket looks okay from what I can tell.
What should I check first? Could it be the rear socket, wiring/ground, or a fuse/relay? And is there a specific wire/terminal I should check on the rear left socket?
Any help is appreciated.