Volume in 2003 yukon denali quit working on radio,

Radio Fuse 15amp located in the under hood fuse box.

Most clock adjustment buttons are located on the GM radio below the volume and on/off knob. Look for the hour and minute buttons below and press corresponding buttons to either set the hours and minutes or both. There will either be AM or PM on LED window indicating morning or night.

Un plugh negative connection of battery cable at night keep it as it is for next morning and connect it start the vehicle but be sure dont switch on the Aircon for next 20 min. if your problem solve other check the fuses and if not ok contact to the dealer.

Rear heat not working ? The blower motor isn't working ? No air coming from the rear vent's ? Is it just a yukon or XL or denali ? What size engine ? 4.8 , 5.3 or 6.0 l Manual or automatic climate control ? Does the blower motor work on any speed ? The front an rear heater system are seperate , have there own electrical circuits . Could have a couple of different systems ,could have a control processor or relay's an a resistor block . Do you know how to test automotive electrical circuit's using a wiring diagram and a DVOM - digital volt ohm meter ? Plus to get at the rear heater-A/C unit you would need to take the right rear trim panel off .
2003 Tahoe No Rear Heat Fix Suburban Yukon XL Repair

The cluster is powered by the radio fuse. Is the radio working?

How to fix the steering wheel options on my steering wheel, for instance the volume for radio, onstar, etc? I have a '03 gmc Yukon denali xl

You may have a stock amplfier in that truck that wont jive with the new radio, check with radio manufacturer or vendor where you got the radio.

one way is to take it to a dealer and let them look up the code. or if the previous owner has the code,

Check you fuses and relays. They are usually the culprits when so many things go out at once.

The built in power amplifier has gone bad and needs to be replaced. You can have the radio repaired, which is cheaper then replacing it. It's common for the OEM radio on the GM to go bad as they draw high current and the heat causes the problem. Good luck and keep me posted.