GM Service Manual Online
For 1990-2009 cars only

The head up display (HUD) is a secondary display system that reflects vehicle information onto the windshield. The HUD system consists of the following:

    • The indicator displays
    • The vehicle speed display
    • The radio/CD display
    • The control switches
    • The adaptive cruise control display
    • Ambient air temperature

Indicator Displays

The HUD displays the following and other arbitrary information generated from vehicle systems:

    • The CHECK GAGES indicator
    • The high beam indicator
    • The km/h (MPH) indicator
    • The low fuel indicator
    • The turn signal indicators
    • Tap Up/Tap Down Gear Selected and Upshift indicator
    • Upshift indicator

Refer to Indicator/Warning Message Description and Operation .

Vehicle Speed Display

The HUD displays the vehicle speed based on information from the vehicle speed sensor. The ECM converts the data from the vehicle speed sensor to a 4,000 pulses/mile signal. The HUD uses the vehicle speed signal circuit (4,000 pulses/mile) from the ECM in order to calculate the vehicle speed. The HUD displays either miles or kilometers as requested from the DIC. The associated indicator (km/h or MPH) illuminates in the IPC.

Ambient Air Temperature

The HUD displays the ambient air temperature based on serial data messages from the HVAC module. The ambient air temperature is displayed in Celsius or Fahrenheit corresponding to the DIC English or Metric setting.

Adaptive Cruise Control

The HUD displays the adaptive cruise control information to the driver. Refer to Cruise Control Description and Operation and Indicator/Warning Message Description and Operation for all the adaptive cruise indicators displayed in the HUD

Radio Display

The HUD displays the following radio information:

    • The radio frequency and the band
    • The CD disc (for multiple changer) and the CD track
    • The cassette symbol

The HUD receives serial data messages from the radio indicating the display mode, the frequency, the band, and the CD track.

Control Switches

The HUD switch consists of the following controls:

    • The image adjustment switch
    • The display dimming switch

The image adjustment switch controls the electric tilt adjust within the HUD. The image adjustment switch is hard wired to the motor within the HUD in order to move the HUD image vertically on the windshield. When the switch is in the up position, the HUD image up control circuit provides voltage to the motor and the HUD image down control circuit provides the ground. When the switch is in the down position, the HUD image down control circuit provides voltage to the motor and the HUD image up control circuit provides the ground.

The HUD brightness is manually adjusted by turning the display dimming switch. Turn the switch all the way to the left in order to turn OFF the HUD display. Turn the switch all the way to the right for maximum display brightness. The HUD receives a serial data message from the BCM indicating the brightness level. When it is determined that it is daytime, the HUD uses both the integrated HUD photocell and the display dimming switch in order to control the dimming. If it is determined that it is nighttime, the HUD uses the display dimming switch only in order to control the dimming.