GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    •  Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    •  Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

HUD Battery Positive Voltage Circuit

--

1

--

HUD Dimming Up Switch Signal Circuit

B3634

1

--

HUD Dimming Down Switch Signal Circuit

B3659

2

--

HUD Ground Circuit

--

1

--

HUD Switch Ground Circuit

--

1

2

--

1. HUD Inoperative

2. HUD Always On

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 on the windshield in front of the driver. Battery positive voltage is the power source to the HUD system. The HUD system can only be enabled when the ignition is active and in RUN position. The HUD receives vehicle information for display via the serial data circuit. The HUD system also receives vehicle and engine speed information via discreet vehicle and engine speed signal circuits. The HUD interfaces with the HUD switch via discreet circuits and the HUD switch inputs to the HUD is low. A press and hold of the dimming up switch greater than 1 sec initiates a smooth increase in the HUD display intensity until the switch is released or maximum intensity is achieved. The HUD does not have a separate Off switch. The HUD is turned OFF using the dimming down switch. A press and hold of the dimming down switch greater than 1 sec initiates a smooth decrease in the HUD intensity until the switch is released or the HUD is turned OFF.

Reference Information

Schematic Reference

Head Up Display Schematics

Connector End View Reference

    •  Displays and Gages Connector End Views
    •  Inline Harness 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. Ignition OFF, disconnect the harness connector at the HUD.
  2. Verify a test lamp illuminates when connected between the HUD dimming down switch signal circuit terminal 12 and B+ while pressing the HUD dimming down switch.
  3. If the test light does not illuminate, test the HUD dimming down switch signal circuit terminal 12 and the ground circuit terminal 6 for an open/high resistance. If the circuits test normal, replace the HUD switch.
  4. If all circuits test normal, test or replace the HUD.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Control Module References for the HUD replacement, setup and programming
    •  Head Up Display Switch Replacement