Grey screen, vertical lines after GMC Update

[RAnthony]

2011 CTS V VLINE VL2. Installed the latest up VLINE update, no problem. Installed the GMC UPDATE immediately after, now I have a grey screen that goes white, then vertical lines. Tried numerous times to reboot the system by unplugging the connector. Turning the ignition off and on.

[admin]

Can you please explain what is the GMC update exactly?

[RAnthony]

Update. Tech sent a reboot file to be loaded on a thumb drive. Followed the instructions on their YouTube video included in the instructions. System back online with the current firmware update.