Where is the turn signal flasher located on a 1997 GMC sonoma pickup?
According to the Auto Zone web site: the flasher is under the dash, near the steering; or, near the cigar lighter, under the dash.
Of course one way of finding it is to turn on the turn signal and track down the clicks. But who needs to find one when it is working?? It the book is wrong (and often is) find someone with the same model and year and ask them to let you listen to their flasher. An interesting way of meeting new people. 
On the Sonoma it is under the lower dash panel, just to the left of the cigarette lighter. To get to it you must remove the ashtray. Then remove screws holding the plastic panel that is below the dashboard. You will see two round "can " shaped flasher units. The one on the right is for the signal lights. The one on the left is for the emergency flashers.
~Michael