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
    • Engine speed display
    • The radio/CD/MP3/Digital Radio Function display
    • The control switches
    • Arbitrary messages/texts

Indicator Displays

The HUD displays the following:

    • CHECK GAGES indicator
    • Engine coolant temperature indicator
    • Engine oil pressure indicator
    • Engine oil temperature indicator
    • G-Force Indicator
    • High beam indicator
    • Km/h (MPH) indicator
    • Low fuel indicator
    • Turn signal indicators
    • Transmission oil temperature
    • Tap Up/Tap down 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 engine control module (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 by the activation of the English/metric button in the DIC switch. The associated indicator (km/h or MPH) illuminates.

Engine Speed Display

The HUD displays the engine speed based on information from the ECM. The HUD uses the engine speed signal circuit from the ECM in order to display the engine speed. Each engine revolution represents input pulses to the ECM. The instantaneous engine speed is calculated by the ECM using the time difference between the 2 input pulses.

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. The HUD receives a serial data messages from the remote playback device - CD changer indicating the current CD disc number and the CD track.

Control Switches

The HUD switch consists of the following controls:

    • HUD image adjustment switch
    • HUD display dimming switch
    • HUD display page switch
    • HUD display mode switch

The vertical image adjust up switch and the vertical image adjust down switch controls the height adjustment of the image on the windshield.

The HUD display dimming switch is used to control the brightness of the HUD display and the forward facing ambient light sensor. Pressing and holding the switch initiates a smooth increase or decrease in HUD intensity until MAX/OFF intensity is achieved.

The HUD display page switch allows a driver to scroll through and select a style of display page

The HUD display mode switch allows the driver to select or sort through the available HUD mode formats.