A clicking noise may be noted from the turn signal flasher after the turn signals are switched off. This is commonly cause by a faulty turn signal switch which will require replacement.Google+
Car Problem Reports
GMC Yukon Turn Signal Switch May Fail and Cause Clicking Noise
GMC Yukon Problem
Average Mileage: 190,000 mi (126,000 mi - 299,000 mi)
Visitor, 1995 GMC Yukon, 155,000 mi
I hear a clicking noise when the directional signal swich is in the off position. Sometimes it stops when I step on the brakes
The turn signal "sound" stays on even though the turn signal itself is not.
Visitor, 2000 GMC Yukon, 180,000 mi
Same exact problem as described.