B3634

DTC B3634

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 B3634
- Head-Up Display (HUD) Dimming Up Switch Signal Circuit Short to Ground.

Diagnostic Fault Information





Circuit/System Description

The head-up display (HUD) dim up switch is a momentary contact switch that adjusts the HUD display brightness. The HUD dim up switch controls the intensity of the brightness. The HUD senses when the dim up switch is active and adjusts the display brightness until the desired intensity is attained. When the HUD dim up switch is pressed and the ignition is in the RUN position, the dim up switch signal to the HUD is low. A press and hold of the dim up switch greater than 1 second initiates a smooth increase in the HUD intensity until the switch is released or maximum intensity is achieved.

Conditions for Running the DTC

The ignition is in RUN.

Conditions for Setting the DTC

The HUD detects that the HUD dim 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 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 dimming up switch is pressed, the HUD display intensity on the windshield and the scan tool Dimming Level parameter percentage increases simultaneously.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the HUD switch.
2. Ignition OFF, test for less than 5 ohms between the ground circuit terminal F and ground.

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

3. Verify the scan tool Dimming Level parameter is less than 95 percent.

• If greater than the specified range, test the signal circuit terminal C 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 C and the ground circuit terminal F. Verify the scan tool Dimming Level parameter is greater than 95 percent.

• If less than the specified range, 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)