No Sound Is Heard. [Vehicles Without Audio Amplifier]

Inspection Procedure 2: No sound is heard. [Vehicles without audio amplifier]

CAUTION: Before replacing the audio visual navigation unit, ensure that the power supply circuit, the ground circuit, and the communication circuit are normal. (Check that the voltage is 10 V or more.)

COMMENTS ON TROUBLE SYMPTOM
If the audio sound is not output, the audio visual navigation unit, audio amplifier, or power supply circuit of audio amplifier may have a problem, or the option coding information may be inconsistent.

PROBABLE CAUSES
- The audio visual navigation unit may be defective
- The audio amplifier may be defective
- Option coding information inconsistency
- Damaged harness wires and connectors

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

STEP 1. Check the audio visual navigation unit operation.

Q: Check the sources from which the sound is not output.

No sound only from radio : Perform Inspection Procedure 6 "The AM/FM Radio Broadcasting cannot be Received." Inspection Procedure 6

No sound only when the CD is played : Perform Inspection Procedure 8 "CD/DVD cannot be Played." Inspection Procedure 8

No sound only when the DVD is played : Perform Inspection Procedure 8 "CD/DVD cannot be Played." Inspection Procedure 8 or Inspection Procedure 9 "Image of a DVD is Played, but no Sound is Played." Inspection Procedure 9

No sound only when the music server is used : Go to Step 8.

No sound from any of the sources : Go to Step 2.

STEP 2. Check the ETACS-ECU coding data.

Use scan tool MB991958 to diagnose the CAN bus lines.







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 the Scan Tool (M.U.T.-III)
2. Turn the ignition switch to "ON" position.
3. Operate the scan tool MB991958 to read the ETACS-ECU option coding information (Refer to Coding Table).
4. Check that the "Number of speaker" is set to "6 speakers" or "4 speakers".

Q: Is the check result normal?

YES : Go to Step 3.

NO : Operate scan tool MB991958 to set the option coding "Number of speaker" to "6 speakers" or "4 speakers" and check the trouble symptom.

STEP 3. Check the MMCS service mode, CAN communication confirmation, and coding data.

1. Display the CAN Communication Confirmation and Coding Data of the MMCS service mode. Service Mode
2. Check if "6 SPEAKER (2 TWEETER)" or "4 SPEAKER" is displayed as the number of installed speakers.

Q: Is the check result normal?

YES : Go to step 4.

NO : Go to step 5.

STEP 4. Check the service data log for the MMCS service mode.

With the service data log of MMCS service mode displayed, check if the service data log for SP (speaker) is displayed. Refer to Service Mode

Q: Is the service data log for SP (speaker) displayed?

YES : Go to step 5.

NO : Go to step 8.

STEP 5. Using scan tool MB991958, diagnose the CAN bus line.

Use scan tool MB991958 to diagnose the CAN bus lines.

1. Turn the ignition switch to "ON" position.
2. Diagnose the CAN bus line.

Q: Is the check result normal?

YES : Go to Step 6.

NO : Repair the CAN bus line.

STEP 6. Using scan tool MB991958, read the CAN box unit diagnostic trouble code.

Check again if the DTC is set to the CAN box unit.

Q: Is the DTC set?

YES : Troubleshoot the MMCS. Diagnostic Trouble Code Descriptions

NO : Go to Step 7.

STEP 7. Using scan tool MB991958, read the ETACS-ECU diagnostic trouble code.

Check if the diagnostic trouble code is set to the ETACS-ECU.

Q: Is the DTC set?

YES : Diagnose the ETACS-ECU. Diagnostic Trouble Code Descriptions

NO : Go to Step 8.

STEP 8. Check the service data log for the MMCS service mode.

1. Display the service data log for the MMCS service mode. Refer to Service Mode
2. Check if the service data log for drive and HDD is displayed.

Q: Is the service data log displayed?

YES (The service data log for drive is displayed.) : Perform Inspection Procedure 8 "CD/DVD cannot be Played." Inspection Procedure 9 or Inspection Procedure 9 "Image of a DVD is Played, but no Sound is Played." Inspection Procedure 9Go to Step 9.

YES (The service data log for HDD is displayed.) : Abnormalities relating to high or low temperature may be present. Check if the audio visual navigation unit can output the sound at the operable temperature. If it cannot output the sound, go to Step 9.

NO : Go to Step 9.

STEP 9. Perform "Network/Connect Line Check" in the MMCS service mode.

1. Display "Network/Connect Line Check" in the MMCS service mode. Refer to Service Mode
2. Check if "DVD Drive OK" is displayed.
3. Check if "HDD Drive OK" is displayed.

Q: Is the check result normal?

YES : Go to Step 11.

NO : Go to Step 10.

STEP 10. Retest the system

Check that the audio sound is output.

Q: Is the check result normal?

YES : The trouble can be an intermittent malfunction.

NO : Go to step 11.

STEP 11. Retest the system

Temporarily replace the audio visual navigation unit and check if the sound is output.

Q: Is the check result normal?

YES : Replace the audio visual navigation unit.

NO : Perform Inspection Procedure 3 "No sound is heard from one of the speakers. [Vehicles without audio amplifier]" Refer to Inspection Procedure 3