Inspection Procedure 5

Inspection Procedure 5: Audio Illuminations Does Not Work Normally.

CAUTION: Before replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.

Center Panel Unit Communication Circuit:

OPERATION
- When the position light is illuminated, the audio illumination is switched to the nighttime illumination.
- When the brightness is adjusted using the combination meter rheostat switch, the audio illumination brightness is also adjusted.

COMMENTS ON TROUBLE SYMPTOM
The center panel unit, radio and CD player, combination meter, or communication line from the radio and CD player to the combination meter may have a problem.

PROBABLE CAUSES
- The combination meter may be defective.
- The radio and CD player may be defective.
- The center panel unit may be defective.
- Damaged harness wires and connectors

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe

STEP 1. Operation check of the center panel unit

Operate the audio control switch of the center panel unit, and check if the audio operates normally.

Q : Is the check result normal?

YES : Go to Step 2.

NO : Refer to Inspection Procedure 4 "The audio does not operate normally by operating the radio and CD player of the center panel unit." Inspection Procedure 4

STEP 2. Check the combination meter.

Check whether the combination meter works normally.

Q : Is the check result normal?

YES : Go to Step 3.

NO : Diagnose the combination meter. Diagnostic Trouble Code Descriptions

STEP 3. Using scan tool MB991958, read the combination meter diagnostic trouble code.

Check again if the DTC is set to the combination meter.

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.




1. Connect scan tool MB991958. Refer to "How to connect scan tool". Scan Tool Connecting
2. Turn the ignition switch to the "ON" position.
3. Check for combination meter DTCs.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q : Is the DTC set?

YES : Diagnose the combination meter. Diagnostic Trouble Code Descriptions

NO : Go to Step 4.

STEP 4. Check center panel unit connector C-124 and combination meter connector C-04 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q : Are center panel unit connector C-124 and combination meter connector C-04 in good condition?

YES : Go to Step 5.

NO : Repair the connector concerned.

STEP 5. Check the wiring harness between center panel unit connector C-124 (terminal 10, 16) and combination meter connector C-04 (terminal 22, 23).

- Check the communication lines for open circuit and short circuit.

NOTE: Also check A/C control panel connector C-123 and joint connector C-101 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If A/C control panel connector C-123 and joint connector C-101 is damaged, repair or replace the connector as described in General (Electrical), Harness Connector Inspection.

Q : Is the wiring harness between center panel unit connector C-124 (terminal 10, 16) and combination meter connector C-04 (terminal 22, 23) in good condition?

YES : Go to Step 6.

NO : Repair the wiring harness.

STEP 6. Check radio and CD player connector C-109 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q : Is radio and CD player connector C-109 in good condition?

YES : Go to Step 7.

NO : Repair the connector concerned.

STEP 7. Check the wiring harness between center panel unit connector C-124 (terminal 4) and radio and CD player connector C-109 (terminal 9).

- Check the communication lines for open circuit and short circuit.

Q : Is the wiring harness between center panel unit connector C-124 (terminal 4) and radio and CD player connector C-109 (terminal 9) in good condition?

YES : Go to Step 8.

NO : Repair the wiring harness.

STEP 8. Replace the center panel unit temporarily, and check the trouble symptom.

Replace the center panel unit temporarily, and check that the audio illumination works normally.

Q : Is the check result normal?

YES : Replace the center panel unit.

NO : Replace the radio and CD player.