Folks: Unplugged battery for a few hours while I installed a new throttle body and other engine items. Upon power up, the clock has lost its time--no surprise; however, as I go into the menu to set it, no numbers appear in the hour or minute fields for me to go up or down with. In other words, I can't set it. So the clock on the display screen of my Yukon Denali just shows " : " A colon with no number before or after. Is this unit fried? If so, how strange. A power cut and it can't be reset. I tried unplugging the battery for 15 seconds to see if I would let me set it. Nope. Same problem. Any suggestions?