Hey guys,
I found this thread/forum after a Google search led me here as I was having the same issue. I signed up so I could reply and tell you what fixed my turn signal issue in hopes that it helps someone else.
Issue: Both right and left rear turn signal failure notifications on the dash. Rapid flash after 3 flashes. All turn signals worked. My truck is a 2014 Silverado, oem tail lights.
Now let’s back up a little. A week ago I had and left rear turn signal fail on me. No big deal right? I did a Google search for a replacement bulb part number and the results I found were a 7443 bulb. I picked up a set of 7443 bulbs, replaced the burnt out bulb and all was good (I did not change both sides). A few days later I get the right and left turn signal failure notification even though both bulbs are working. After racking my brain for a few days, checking over the wiring harness and the circuit board, I took a closer look at the bulbs. I found that my OEM bulb was actually a 7444 and Google told me 7443. The difference in the two bulbs is the voltage/watt draw. I went to the parts store and bought 4 new 7444 bulbs and replaced the brake light bulbs and the turn signal bulbs. Doing this resolved my issue. Changing the brake bulbs was probably unnecessary, but for $8 I went ahead and changed them while I had the tail lights out. My theory is the Silverado computer freaked out because the left turn signal (7443) and the right turn signal (7444) were pulling different volt/watts causing it to throw the message on both sides. So if you're having this issue, I would recommend replacing all 4 bulbs with quality 7444 bulbs, especially since it's very possible that you too could have mixed bulbs in the taillights. This was a $16 fix for me. I hope this helps anyone else having this issue.