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.

DTC Descriptor

DTC B3659: Head-Up Display (HUD) Dimming Down Switch Short to Ground

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

HUD Dimming Down Switch Signal Circuit

B3659

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HUD Switch Ground Circuit

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Circuit/System Description

The head-up display (HUD) dimming down switch is a momentary contact switch that adjusts the HUD display brightness. The HUD dimmer down switch controls the intensity of the brightness. The HUD senses when the dimming down switch is active and adjusts the display brightness until the desired intensity is attained. When the HUD illumination reaches the minimum intensity, the HUD will turn off the display by the next dimming down switch input. The HUD does not have a separate OFF switch. The HUD is turned OFF using the dimming down switch. When the HUD dimming down switch is pressed and the ignition is in the RUN position, the dimming down switch signal to the HUD is low. 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.

Conditions for Running the DTC

The ignition is in RUN.

Conditions for Setting the DTC

The HUD detects that the HUD dimming down switch signal circuit is low for greater than 60 seconds.

Action Taken When the DTC Sets

The HUD ignores the malfunctioning switch circuit.

Conditions for Clearing the DTC

    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • The history DTC clears after 40 malfunction-free warm-up cycles.

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 does not illuminate when connected between the HUD dimming down switch signal circuit terminal 12 and B+.
  3. If the test light illuminates, test the HUD dimming down switch signal circuit terminal 12 for a short to ground. If the circuit tests normal, replace the HUD.
  4. If all circuits test normal, test or replace the HUD switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Control Module References
    •  Head Up Display Switch Replacement