2001 GMC Yukon Owner's Manual - Page 127

Electrochromic Inside Rearview Mirror with Compass and Temperature Display (If Equipped) When on, an electrochromic mirror automatically dims to the proper level to minimize glare from lights behind you after dark. Temperature Display Pressing the TEMP button once briefly will toggle the compass/temperature reading on and off. To alternate the temperature reading between Fahrenheit and Celsius, press and hold the TEMP button for three seconds until the display blinks "F_" and "C_". Press and release the TEMP button to toggle between the Fahrenheit and Celsius readings. After five seconds of inactivity, the display will stop flashing and stay at the last setting. If an abnormal reading is displayed, please consult your dealer. The mirror also includes a display of both the compass and the temperature in the upper right corner of the mirror face. The dual display can be turned on or off by briefly pressing either COMP or TEMP button. 2-49