Bulletin Number: 15-221-18R; Revised 02/12/21
Page 4 of 45
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4. Do you hear audio? Can you change the volume? Can you change the audio source?
5. Does pressing hard keys awake the display screen?
6.
When pressing the screen – do you hear a beep (conclusion can only be drawn when hearing
a beep)?
7. Check CAN for trouble.
Based on the data collected follow the service manual to complete diagnostic and isolate the concern
leading to a repair.
CONDITION# 0.3
HMI partially shown:
CAUSE:
1.
Audio output means the services are working => the microprocessor is operating.
2.
For vehicles not equipped with an external amp, a beep sound when the screen is pressed
indicates the microprocessor is running and receiving input from the touch panel. Possibly
a backlighting issue. For Harmon Kardon amplifier vehicles, if a beep is not heard this
could mean the amplifier is not communicating or, the system is not sending a request to the
amplifier to play a beep. In this scenario, it is hard to draw a conclusion.
3.
Certain buttons/labels are dependent on software configuration or CAN messages. Knowing
what is shown and what isn’t shown helps to diagnose the root cause.
4.
Audio services are running, indicating the microprocessor is not locked up.
5.
If the issue is addressed, this points to something causing the HMI to not update correctly,
helps narrow down the issue to possibly a timing issue or an issue with the HMI.
RECOMMENDATION:
List of things to try:
1. Do you hear audio? Can you change audio source?
2.
When you press the screen – do you hear a beep (conclusion can only be drawn when hearing
a beep)?
3.
Are button labels there - no/some/all labels?
4.
Is metadata shown (album, name of song, …) on the display?
5. Can you change between screens using the hard keys?
a. When you go back to blank screen – still in that state?
Based on the data collected follow the service manual to complete diagnostic and isolate the concern
leading to a repair.
