B3621

DTC B3621

Diagnostic Instructions

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

DTC Descriptor
DTC B3621
- Head-Up Display (HUD) Down Switch Circuit Short to Ground

Diagnostic Fault Information





Circuit/System Description

The head-up display (HUD) image down switch is used to vertically adjust the HUD image on the windshield to accommodate various vehicle operator heights. The HUD monitors the image down switch signal circuit in order to adjust image positions. When the HUD image down 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 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 (Head-Up Display Schematics)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Head-Up Display Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information.

Circuit/System Verification

Ignition ON, verify that when the HUD image down switch is pressed and released the HUD scan tool Adjust Display Down 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 ohms between the HUD switch ground circuit terminal F and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Adjust Display Down Switch parameter is Inactive.

• If not Inactive, test the signal circuit terminal K for a short to ground. If the circuit tests normal, replace the HUD.

4. Install a 3A fused jumper wire between the signal circuit terminal K and ground. Verify the scan tool Adjust Display Down Switch parameter is Active.

• 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.

5. If all circuits test normal, test or replace the HUD switch.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Control Module References (Programming and Relearning)
* Head Up Display Switch Replacement (Head Up Display Switch Replacement)