2010 Cadillac STS Owner's Manual - Page 220

The Ignition is On and the HUD Image Cannot Be Seen Check to see if: ... The following messages may appear in the HUD: SPEED ALERT The HUD unit is covered. The brightness is adjusted properly. The HUD display is adjusted to the proper height. Ambient light in the direction the vehicle is facing is low. A fuse is blown. See Fuses and Circuit Breakers on page 6‑117. Posted Speed Advisory Speed When the Speed Advisor feature is turned on, HUD displays either the posted or advisory speed as determined by the information on the map disc in the navigation system. To turn the Speed Advisor on or off, see DIC Operation and Displays on page 4‑70. . The windshield is part of the HUD system. See Windshield Replacement on page 6‑50. 4-40