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 B3620: Head-Up Display (HUD) Image Up Switch Signal Circuit Short to Ground

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

HUD Image Up Switch Signal

B3620

1

1

HUD Image Down Switch Signal

B3621

1

1

HUD Battery + Circuit

1

1

--

HUD Ground Circuit

--

1

--

Dimmer/HUD Switch Ground Circuit

--

1

1

1. Head-Up Display (HUD) Malfunction.

Circuit/System Description

The head-up display (HUD) image down or image up switch are used to vertically adjust the HUD image on the windshield to accommodate various vehicle operator heights. The HUD monitors the image down or image up switch signal circuit in order to adjust image positions. When the HUD image down or image up switch is depressed and the ignition is in the RUN position, the switch signal to the HUD is low.

Conditions for Running the DTC

The ignition is in RUN.

Conditions for Setting the DTC

The HUD detects that the HUD image up 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

Component Connector End Views

Description and Operation

Head Up Display (HUD) Description and Operation

Electrical Information Reference

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

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Verification

Ignition ON, verify that when the HUD image up switch is pressed and released the HUD scan tool Adjust Display Up Switch parameter toggles between Active and Inactive.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the HUD switch.
  2. Test for less than 5.0 ohm between the low reference circuit terminal 1 and ground.
  3. If greater than the specified range, test the low reference circuit for an open/high resistance.
  4. Ignition ON, verify the scan tool Adjust Display Up Switch parameter is Inactive.
  5. If not Inactive, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the HUD.
  6. Install a 3A fused jumper wire between the switch signal circuit terminal 2 and the low reference circuit terminal 1. Verify the scan tool Adjust Display Up Switch parameter is Active.
  7. If not Active, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HUD.
  8. 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