Turn signal causes flasher to click fast?

Check all grounds. May be abad turn signal switch, sounds like you have covered the usual suspects, if grounds are good, all fuses are good it could be the switch here is a guide to help check for power and the blinker wiring diagrams so you can see what fuses to check and the outputs of the switch.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

The fuse panel identifications are below. Check out the diagrams (Below). Please let us know what happens.

I had the same problem. I took the steering wheal off and used a light bulb tester under the turn signal switch on the green and white wire. The light went on and the flasher worked at a normal speed. Then I took the signal switch apart and filed the contact with a point file and that solved the problem.

Excellent addition to this thread! Please feel free to use 2CarPros anytime!