Head Up Display Malfunction
Head-Up Display Malfunction
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.
Diagnostic Fault Information
Circuit/System Description
The head-up display is a secondary display system capable of reflecting important vehicle information onto the windshield. The vehicle information is displayed using virtual imaging and is reflected on the windshield in front of the driver. Battery positive voltage is the power source to the head-up display. The head-up display can only be enabled when the ignition is active and in RUN position. The head-up display receives vehicle information for display via the serial data circuit. The head-up display switch signal circuit is pulled up to battery voltage in the head-up display. The head-up display also provides the head-up display switch with a low reference. The head-up display switch is a momentary contact switch that connects a series of resistors in a resistor ladder format. The head-up display monitors the head-up display switch signal circuit to determine the head-up display switch inputs. Each switch state PAGE, UP, DOWN corresponds to a certain resistance value. The head-up display determines the switch pressed by the voltage drop across the resistors. The head-up display intensity can be changed by using the head-up display dimming switch. The head-up display is turned OFF using the dimming switch. The head-up display does not have a separate Off switch.
Reference Information
Schematic Reference
Head-Up Display Schematics Head-Up Display Schematics
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
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 Control Module References for scan tool information
Special Tools
J 33431-C - Signal Generator and Instrument Panel Tester
Circuit/System Verification
Ignition ON, verify that when the head-up display dimming switch is change for minimum to maximum position the scan tool Dim Select Switch parameter changes from 1-12.
Circuit/System Testing
Head-Up Display Inoperative
1. Perform Info Display Pattern 1 Check test with the scan tool, verify all pixels on head-up display are turned On or Off.
• If not within the specified range, replace the K78 Head-Up Display Module.
2. Ignition OFF, disconnect the harness connector at the K78 Head-Up Display Module.
3. Ignition OFF, test for less than 30 ohms between the head-up display ground circuit terminal 6 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
4. Ignition ON, verify a test lamp illuminates when connected between the B+ circuit terminal 4 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If all circuits tests normal, replace the K78 head-up display module.
5. Ignition OFF, reconnect the K78 head-up display module.
6. Disconnect the S27 head-up display switch.
7. Connect a fused jumper wire between the signal circuit terminal 3 and ground. Verify the scan tool Dim Select Switch parameter displays Short.
• If not the specified value, test the dimming signal switch circuit for a short to voltage or an open/high resistance. If all circuits test normal, replace the K78 head-up display module.
8. Connect the J 33431-C - generator and tester or a similar variable resistance tool and dial in from 30-920 ohms while observing the scan tool Dim Select Switch parameter. Verify that the parameter display changes from 1 through 12.
• If not the specified range, replace the K78 head-up display module.
9. Test or replace the S27 head-up display switch.
Component Testing
Static Test
1. Ignition OFF, disconnect the harness connector at the S27 Head-Up Display Switch.
2. Test for 5.8-6.2k ohms between the signal terminal 6 and the low reference circuit terminal 1.
• If not within the specified range, replace the S27 Head-Up Display Switch.
3. Test for 550-650 ohms between the signal terminal 6 and the low reference circuit terminal 1 while pressing the Page switch.
• If not within the specified value, replace the S27 Head-Up Display Switch.
4. Test for 1.5-1.7k ohms between the signal terminal 6 and the low reference circuit terminal 1 while pressing the Up switch.
• If not within the specified value, replace the S27 Head-Up Display Switch.
5. Test for 2.4-2.6k ohms between the signal terminal 6 and the low reference circuit terminal 1 while pressing the Down switch.
• If not within the specified value, replace the S27 Head-Up Display Switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Head-Up Display Replacement Head-Up Display Replacement
* Head-Up Display Dimmer Switch Replacement Head-Up Display Dimmer Switch Replacement
* Control Module References Control Module References for instrument cluster replacement, programming and setup