Kenwood KDC x492 blank screen but accepts and ejects CDs...?

need car info ... but my guess is you have a 2003-up GM product and didn't buy the Data bus module. there are harnesses that will plug in ... but if you look at the factory side of where the red wire comes out ... there isn't one . the GMs are turned on/off by a digital signal . hope this guess is right .... if not, edit with car info.