B3634

DTC B3634

Diagnostic Instructions

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



DTC Descriptor
DTC B3634
- Head-Up Display (HUD) Dimming Up Switch Short to Ground




Diagnostic Fault Information






Circuit/System Description

The head-up display (HUD) dimming switch is a momentary press switch that adjusts the HUD display brightness. The HUD dimming switch controls the intensity of the brightness. The HUD switch dimming input is pulled up to 5 volts in the HUD. The HUD dimming switch is pulled down to ground via a 10K potentiometer. When the HUD dimming switch is pressed and the ignition is in the RUN position, the dimming switch signal to the HUD is low. The HUD senses when the dimming switch is active and adjusts the display brightness until the desired intensity is attained.


Conditions for Running the DTC

The ignition is in RUN.


Conditions for Setting the DTC

The HUD detects that the HUD dimming 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 (Head Up Display Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

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

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning)for Scan Tool Information


Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the head-up display (HUD) switch.
2. Test for less than 1.0 ohm of resistance between the low reference circuit terminal 3 and ground.

• If greater than the specified value, test the low reference circuit for an open/high resistance.

3. Ignition ON, test for 4.8-5.2 volts between the illuminated display signal circuit terminal 6 and ground.

• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. 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 (Verification Tests) after completing the diagnostic procedure.

* Head Up Display Switch Replacement (Head Up Display Switch Replacement)
* Control Module References (Programming and Relearning)for the HUD replacement, setup and programming