The flasher relay is actually built-into the base of the big fuse block under the hood and they are not serviceable from what I have seen.
The sound comes from the stereo through the front speakers.
When I swapped factory stereo to a different (better) factory stereo, the sound came-with and was much more pleasing.
The WT trim does not have the DIC controls to change the tones or volume of the tones, but all the settings reside on the stereo.
Weird, I know.

 

Correct^ On the NNBS and up they stopped using an actual flasher module. You could have the module re-flashed, but that is expensive and some dealers may not do it, as it sort of is part of the safety system...

 

So what does the flasher relay mounted in the fuse block base actually do? It activates and deactivates in time with the signals. The brakes pick up the relay also. The real reason for my post is that my driver side front and rear turn signals and rear brake lights do not work, have the rapid flash. New bulbs. Good ground (the parking filament works, both front and rear both upper and lower)
Continuity all the way from socket to the BCM connectors (yes I crawled under the dash, disconnected each connector from the BCM and using a straight pin clamped in my multimeter alligator clip poked in each blasted hole until I got continuity from both the front and rear. Unfortunately I didn't get the actual ohm reading, just the tone. Front and rear were on different connectors, and the wire colors were DIFFERENT than at the sockets!?!?!? Would the relay in the fuse block base have anything to do with the lights not working?