You're going to need to enter the service mode and make note of any and all errors that show up.
Select the car icon on the bottom left of the screen. Next, select the software icon on the bottom of the listed options on the left side of the screen. Then, the screen will display a pic of the car along with the model, mileage, software version, etc. From that screen you'll need to long press the Model # beneath the pic. When prompted enter "service". It will lead you to the service menu where you can check what alerts are in the system.
Unfortunately, I don't believe you can do this while in valet mode. You're going to need the current owner to exit valet mode to do this.