We primarily fix the touchscreen not responding on the Cadillac CUE head unit by replacing the entire top glass touchscreen element.
A black screen is unrelated to the touchscreen. The Cadillac CUE gets the video signal from the HMI Module (Human Machine Interface). When that doesn't work properly, it can result in a black screen when the units are powered on.
The first step is to check the battery. If the battery has a low voltage charge or is failing, there might not be enough voltage to energize the HMI module. You can get your vehicle's battery tested at any auto parts store and they'll let you know if it needs to be replaced or not.
The next step is to check all Display, Radio, and HMI-related fuses. Check your owner's manual to see where they're located for your vehicle. We recommend pulling them out to see not just if it's blown but also if there is any corrosion or debris in the socket where those fuses are installed.
Lastly, if the screen is still black, chances are the HMI needs to be replaced and reprogrammed.
Please note: If a Toyota Prius MFD (Years 2004-2009) has a black screen chances are that the unit itself has power loss. Especially if it's working intermittently and powering on/off or just not powering on at all.