For 1990-2009 cars

### 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.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
HUD Switch Signal | 1 | 1 | B3567 01 | B3567 59
HUD Dimmer Switch Signal | 1 | 1 | 1 | --
HUD switch Low Reference | -- | 1 | 1 | --
1. HUD Malfunction

### Circuit/System Description

The head-up display (HUD) is a display system that optically projects vehicle information onto the windshield. The HUD has an electric tilt adjust that is controlled by the up and down switches. Operating these switches directs the motor to move the HUD image up or down on the windshield. The HUD is equipped with a page switch that scrolls through multiple messages present on the HUD. The HUD is also equipped with automatic dimming. Dimming is controlled by a HUD dimmer switch. All three switches control the HUD by grounding the HUD switch input signals. The dimmer switch uses a variable resistor to control the HUD intensity where the lower the resistance, the brighter the HUD display.

### 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

1. Ignition ON, verify that the HUD image is displayed on the windshield.

⇒ | If the HUD image is not displayed, refer to HUD Inoperative.

2. Ignition ON, verify that when the HUD switches are pressed and released the HUD scan tool parameters toggle between Active and Inactive.

⇒ | If the parameters do not toggle between Active and Inactive, refer to HUD Switch Malfunction.

### Circuit/System Testing

#### HUD Inoperative

1. Ignition OFF, disconnect the harness connector at the HUD switch.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 3 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HUD.

3. Verify the scan tool Display Dimming parameter is greater than 98 percent.

⇒ | If less than the specified range, test the signal circuit terminal 2 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 2 and the low reference circuit terminal 3. Verify the scan tool Display Dimming parameter is less than 2 percent.

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

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

#### HUD Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the HUD switch assembly.
2. Ignition OFF, test for less than 5 ohms between the low reference terminal 3 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance.

3. Ignition ON, verify that all of the scan tool HUD Switch parameters are Inactive.

⇒ | If any is not Inactive, test the signal circuit terminal 6 for a short to ground. If the circuit tests normal, replace the HUD.

4. Ignition ON, install a 3-amp fused jumper wire between the signal circuit terminal 6 and ground. Verify the scan tool HUD Switch parameters are Active.

⇒ | If any are 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 the circuits test normal, test or replace the HUD switch assembly.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Head Up Display Switch Replacement

• | Control Module References for HUD replacement, setup, and programming