GM Service Manual Online
For 1990-2009 cars only

The head-up display (HUD) is a secondary display system that optically projects critical vehicle information onto the windshield. The head-up display (HUD) system has an electric tilt adjust that is controlled by the HUD up/down switch. Moving this switch directs the motor to move the HUD image up or down on the windshield. The HUD is also equipped with automatic dimming which gives the HUD the ability to sense outside light conditions, via a photo-cell and automatically adjusts the brightness levels. You may manually adjust the HUD image brightness by moving the HUD dim switch.

The HUD displays the following images:

    • The speedometer reading (speed up to 120 mph)
    • The turn signal indicators
    • The high beam indicator
    • The low fuel indicator
    • The check gages indicator
    • The radio frequency, including AM, FM, CD, and Tape
    • Backup vehicle speed
    • Values in english or metric units

Speedometer

The HUD receives a class 2 message from the powertrain control module (PCM) indicating vehicle speed.

LH Turn Signal and RH Turn Signal Indicator Inputs

The left and right turn indicators are driven by hardware inputs from the exterior lighting system. The signal is active when the circuit is high (12 volts) and inactive when circuit is open. During hazard mode, both the right and left turn signal circuits are active high, causing both the right and left turn signal indicators to illuminate at the same time.

High Beam Indicator Input

The HUD receives a class 2 message from the BCM with that the high beams have been requested.

Low Fuel

The HUD receives a class 2 message from the IPC indicating low fuel.

CHECK GAGES Inputs

The IPC monitors different inputs and vehicle messages and sends the information to the HUD, via a class 2 message. The HUD illuminates the CHECK GAGES indicator when it receives certain information from the IPC.

The HUD will illuminate the Check Gages indicator for the following messages:

    • Low oil pressure
    • Coolant temp hot
    • Charging system/generator fault
    • Low brake fluid level
    • Parking brake
    • Voltage
    • Brake failure

Radio

The HUD receives a class 2 message from the radio indicating radio frequency, including AM, FM, CD, and Tape.

Backup Vehicle Speed

The HUD receives a class 2 message from the BCM indicating backup vehicle speed.

HUD English/Metric Input

The HUD illuminates the speedometer in either english (mph) or metric (km/h) units depending upon the class 2 message received from the IPC.