Radio

check the fuse sounds like a short

check this .....https://www.bing.com/videos/search?q=2015+GMC+Terrain+SLE1+raido+blank+screen+problem&&view=detail&mid=FA99BB98E4C0101E1535FA99BB98E4C0101E1535&rvsmid=A6950EF63F0097C1D46CA6950EF63F0097C1D46C&FORM=VDRVRV

Went to my mechanic, had fuse checked. Not problem. Also read about how cellphone updates and car companies don't always sync together. Service mgr. told me my that rubbish.

Okey let me ask you this question. Did your mechanic check to see if the fuse that controls the radio was even getting power? Not just pull it out to see if it was blown and put it back in? To do this realize each every fuse gets power from one side of the fuse to that passes through the fuse to the other. Basically the fuse acts as a inline connection or bridge and will blow if it begins to over heat due to a short in that system and will burn inside to protect the system. Did the mechanic probe the fuse socket with a tester (12 Volt tester would work or multi meter ) to see that at least one side of the fuse socket was getting power without the fuse in place ? if not have this done or do it yourself...........To do this pull the fuse and ground one end of the 12 volt test light with the clip to a good ground and with the probe end touch each end of the socket where the fuse plugs in . one side should light up the test light. if it doesn't then the souse that feeds that fuse is faulty not the fuse itself. If it does light up then the fuse is getting power and where the power goes to is faulty. Let me know what happens. If you want to use a meter watch this video to learn how one works first..... https://www.bing.com/videos/search?q=how+to+test+automotive+fuse+socket+is+getting+power&&view=detail&mid=BD937E3E7AEF0AA125FABD937E3E7AEF0AA125FA&rvsmid=DD587FB82D888502FE32DD587FB82D888502FE32&FORM=VDQVAP

A dealer will tend to replace the part they think that isn't working first ( costly ) and if it doesn't work will try to figure out why. However the part that you didn't need will still be charged and the part that wasn't failed or broken will not be reinstalled or returned. This is the main reason I do my own repairs most of the time. The procedures of a dealer are not always cost effective or correct. This has happened to me twice in the past. Once with a mass air flow that was not faulty ( a $500 part ) and one with a cluster. Both times they were wrong in replacing the part and had to go above the service manager to get my unnecessary charge reimbursed back to me by proving the fault was not the part they thought causing the problem or the code stored.