My dvd has sound but no picture - Yukon Denali GMC Cars & Trucks

Hi robert, if you are referring to a car dvd player then first check the wiring of your unit. there could be a picture mute/park brake wire that needs to be grounded. this feature acts as an enable for the picture on your dvd player. next check that you have set the correct system type for your region e.g. pal, ntsc,secam. this will be a button found on your remote control of dvd unit. next try a master reset on the unit. thereafter consult with your installer before taking unit for repairs. cheers!