GM Service Manual Online
For 1990-2009 cars only

Diagnostic Fault Information

Important: Always perform the Diagnostic System Check - Vehicle

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

HUD Battery Voltage Circuit

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2

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--

HUD Ground Circuit

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2

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HUD Switch Ground Circuit

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1

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1. Head Up Display (HUD) Always On

2. Head Up Display HUD Inoperative

Circuit/System Description

The head up display (HUD) is a secondary display system capable of reflecting important vehicle information onto the windshield. The vehicle information is displayed using virtual imaging and is reflected off the windshield in front of the driver. Battery positive voltage is the main power source for the HUD system. However, the HUD system can only be enabled when the ignition is active and in the RUN position. The HUD system receives all vehicle information to be displayed via the class 2 serial data circuit. The HUD system interfaces with the HUD switch via discreet circuits. The HUD switch is a normally open switch and ground is provided from within the HUD switch when any switch press occurs.

Reference Information

Schematic Reference

    •  Head Up Display Schematics
    •  Interior Lights Dimming Schematics

Connector End View Reference

    •  Instrument Panel, Gages, and Console Connector End Views
    •  Lighting Systems Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Scan Tool Data List

Circuit/System Testing

  1. With the ignition OFF, turn the HUD dimmer down switch to the OFF position.
  2. If the HUD turns OFF, check for intermittent and poor connection at the harness connector of the HUD.
  3. Disconnect the HUD switch
  4. Turn the ignition ON, with the engine OFF.
  5. If the HUD does not turn OFF, replace the head up display (HUD).
  6. Connect a test lamp between the ground circuit of the HUD switch and battery positive voltage.
  7. If the test lamp does not illuminate, check the HUD switch ground circuit for an open or a high resistance.
    If the HUD switch ground circuit test normal, replace the HUD switch.
  8. Connect a test lamp between the HUD dimmer down switch signal circuit and battery positive voltage while pressing the HUD dimmer down switch.
  9. If the test lamp does not illuminate, check the HUD dimmer down switch signal circuit for an open or a high resistance.
    If the HUD dimmer down switch signal circuit tests normal, replace the HUD switch.

Repair Instructions

Important: Always perform the CELL LINK 143214 after completing the diagnostic procedure.

    •  Head Up Display Switch Replacement
    •  Control Module References