2003 GMC Sonoma Owner's Manual - Page 169

Setting the Time for Radios with Radio Data Systems (RDS) Your radio may have a button marked with an H or HR to represent hours and an M or MIN to represent minutes. Press and hold the hour button until the correct hour appears on the display. AM or PM will also appear on the display. Press and hold the minute button until the correct minute appears on the display. The time may be set with the ignition on or off. To synchronize the time with an FM station broadcasting Radio Data System (RDS) information, press and hold the hour and minute buttons at the same time for two seconds until UPDATED and the clock symbol appear on the display. If the time is not available from the station, NO UPDAT will appear on the display instead. RDS time is broadcast once a minute. Once you have tuned to an RDS broadcast station, it may take a few minutes for your time to update. AM-FM Radio Playing the Radio PWR (Power): Press this knob to turn the system or1 and off. VOL (Volume): Turn the knob decrease volume. to increase or to RCL (Recall): Press this knob to switch the display between time and radio station frequency. Time display is available with the ignition turned off. 3-42