Audio System Symptom Troubleshooting - Audio illumination (LCD back lights, buttons) do not come on, or vague vision

Audio illumination (LCD back lights, buttons) do not come on, or vague vision


1.With the ignition switch ON (II), check to see if the problem appears when turning the combination light switch ON.

Does the problem appear?


YES - Go to 2.

NO - Operation is normal.n


2.Remove the audio-HVAC-display module, and check for the proper connection of the audio unit connector A (20P).

Is it connected properly?


YES - Go to 3.

NO - Reconnect the connector, and recheck the problem.n


3.Turn the combination light switch ON to see if the light-on indicator comes on.

Does it come on?


YES - Go to 4.

NO - With gauge control module self-diagnosis, check if the indicator comes on. If not, inspect the harness between the audio unit and gauge control module.n


4.Operate the dash light brightness controller to check for the illuminating function.
  • The illumination only function normally in the gauge control module, but it does not on part of the LCD back lights and part of the buttons from the audio unit are not illuminated.
  • The illumination on the audio unit, both LCD back lights and all lights for the buttons stay off.

Is illumination as described?


YES - Faulty audio unit.n

NO - Go to 5.


5.Check that both LCD back lights and all lights for the buttons stay off.

Do they all stay off?


YES - Go to 9.

NO - Go to 6.

6.Check the only the LCD back lights stay off.

Do they all stay off?


YES - Faulty audio unit.n


NO - Go to 7.


7.Check the part of the LCD back lights, not the entire LCD, are off.

Are part of the LCD back lights off?


YES - Faulty front printed circuit board.n


NO - Go to 8.


8.Check that all the lights for the buttons are off.

Are they all off?


YES - Go to 9.


NO - Faulty front printed circuit board.n


9.With the combination light switch off, measure the voltage between the No. 9 and No. 20 terminals, and between the No. 19 and No. 20 terminals of the audio unit connector A (20P).

Is there 12 V at the No. 9 terminal, and 0 V at the No. 19 terminal?


YES - Go to 10.


NO - Check the harness between the No. 9 and No. 20 terminals of the audio unit for an open circuit or poor connection. n

10.Remove the audio-HVAC-display module, and inspect the continuity between the terminals as specified in the check list.

Auto A/C
CONN-ECTOR CN-4
No.11 		CN-4
No.5 		CN-4
No.3 		CN-4
No.4 
CN-4
No.1 		2 ohms or less No continuity No continuity No continuity 
CN-4
No.4 		No continuity 2 ohms or less No continuity No continuity 
CN-4
No.2 		No continuity No continuity No continuity No continuity 
CN-3
No.3 		No continuity No continuity 2 ohms or less No continuity 
CN-3
No.1 		No continuity No continuity No continuity 2 ohms or less 
CN-4
No.16 		No continuity No continuity No continuity No continuity 
CN-2
No.7 		No continuity No continuity No continuity No continuity 


Manual A/C
CONN-ECTOR CN-4
No.11 		CN-4
No.5 		CN-4
No.3 		CN-4
No.4 
CN-4
No.1 		2 ohms or less No continuity No continuity No continuity 
CN-4
No.4 		No continuity 2 ohms or less No continuity No continuity 
CN-4
No.2 		No continuity No continuity No continuity No continuity 
CN-3
No.3 		No continuity No continuity 2 ohms or less No continuity 
CN-3
No.1 		No continuity No continuity No continuity 2 ohms or less 
CN-4
No.16 		No continuity No continuity No continuity No continuity 
CN-1
No.22 		No continuity No continuity No continuity No continuity 

CN-1: Climate control unit or heater control panel 22P connector
CN-2: Climate control unit or heater control panel 16P connector
CN-3: Front printed circuit board 10P connector.
CN-4: Front printed circuit board 20P connector.