2003 GMC Sonoma Owner's Manual - Page 114

Outside Convex Mirror A convex mirror's surface is curved so you can see more from the driver's seat. Outside Heated Mirrors Your vehicle may be equipped with heated outside rearview mirrors. The heated mirror button is located to the lower right of the mode knob on the climate control system. The button has an indicator light to indicate if the heated mirror feature is on or off. A convex mirror can make things (like other vehicles) look farther away than they really are. If you cut too sharply into the right lane, you could hit a vehicle on your right. Check your inside mirror or glance over your shoulder before changing lanes. When the heated mirror feature is turned on, the defogger will warm the mirrors to help clear them of snow or condensation. The heated mirror feature will turn off automatically when the mirror is clear. 2-39