2012 GMC Sierra Owner's Manual - Page 206

6-6 Lighting Holding the turn signal lever for more than one second will cause the turn signals to flash until you release the lever. The lever returns to its starting position whenever it is released. If after signaling a turn or a lane change the arrows flash rapidly or do not come on, a signal bulb could be burned out. Have the bulbs replaced. If the bulb is not burned out, check the fuse. See Fuses and Circuit Breakers on page 10‑44. Turn Signal On Chime If the turn signal is left on for more than 1.2 km (0.75 mi), a chime will sound at each flash of the turn signal and the message TURN SIGNAL ON will also appear in the Driver Information Control (DIC). To turn the chime and message off, move the turn signal lever to the off position. Fog Lamps # (Fog Lamps): Press to turn the fog lamps on or off. A light will come on in the instrument panel cluster. When the fog lamps are turned on, the parking lamps automatically turn on. When the headlamps are changed to high beam, the fog lamps also go off. When the high-beam headlamps are turned off, the fog lamps will come on again. Some localities have laws that require the headlamps to be on with the fog lamps. For vehicles with fog lamps, the control is located next to the exterior lamps control on the instrument panel, to the left of the steering column. The ignition must be in the ON/RUN position for the fog lamps to come on. Auxiliary Roof-Mounted Lamp If the vehicle has this feature, this button includes wiring provisions for a dealer or a qualified service center to install an auxiliary roof lamp.