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 components:

    • The indicator displays
    • The speedometer display
    • The control switches

Indicator Displays

The HUD displays the following indicators:

    • CHECK GAGES
    • High beam
    • km/h (MPH)
    • Left and right turn signals

For further information on these indicators, 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 PCM converts the data from the vehicle speed sensor to a 4000 pulses/mile signal. The HUD uses the vehicle speed signal circuit (4000 pulses/mile) from the PCM in order to calculate the vehicle speed. The HUD displays either miles or kilometers as requested by the activation of the DIC Eng/Met button.

Control Switches

The HUD switch consists of the following control switches:

    • Image adjustment switch
    • 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 sliding the display dimming switch. Slide the switch all the way down in order to turn off the HUD display. Slide the switch all the way up for maximum display brightness. The instrument panel integration module (IPM) (w/CJ2) or the HVAC control module (w/C67) monitors the ambient light sensor. The HUD receives a class 2 message from the IPM or the CCP 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.