Inspection Procedure 2

INSPECTION PROCEDURE 2: No Sound Is Heard. [Vehicles With Audio Amplifier]

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

Audio Amplifier System Circuit (Part 1):

Audio Amplifier System Circuit (Part 2):

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

PROBABLE CAUSES
- The radio and CD player may be defective
- The audio amplifier may be defective
- Option coding information inconsistency
- Damaged harness wires and connectors

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe
- 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 ETACS-ECU coding data.







1. Operate the scan tool MB991958 to read the ETACS-ECU option coding information.
2. Check that the "Number of speaker" is set to "Premium."

Q: Is the check result normal?

YES : Go to Step 2.

NO : Operate scan tool MB991958 to set the option coding "Number of speaker" to "Premium," and check the trouble symptom.

STEP 2. Check audio amplifier connector D-29 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is audio amplifier connector D-29 in good condition?

YES : Go to Step 3.

NO : Repair or replace the damaged component(s).

STEP 3. Check the ground circuit to the audio amplifier. Measure the resistance at audio amplifier connector D-29.

1. Disconnect audio amplifier connector D-29, and measure the resistance available at the wiring harness side of the connector.







2. Measure the resistance between terminal 24 and ground.

OK: The resistance should be 2 ohms or less







3. Measure the resistance between terminal 31 and ground.

OK: The resistance should be 2 ohms or less







4. Measure the resistance between terminal 32 and ground.

OK: The resistance should be 2 ohms or less

Q: Is the measured resistance 2 ohms or less?

YES : Go to Step 5.

NO : Go to Step 4.

STEP 4. Check the wiring harness between audio amplifier connector D-29 (terminal 24, 31, 32) and ground.

- Check the ground wires for open circuit.

Q: Is the wiring harness between audio amplifier connector D-29 (terminal 24, 31, 32) and ground in good condition?

YES : The trouble can be an intermittent malfunction.

NO : The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary.

STEP 5. Check the power supply circuit to the audio amplifier. Measure the voltage at audio amplifier connector D-29.

1. Disconnect audio amplifier connector D-29, and measure the voltage available at the wiring harness-side connector







2. Measure the voltage between terminal 25 and ground.

OK:Battery positive voltage.







3. Measure the voltage between terminal 35 and ground.

OK:Battery positive voltage.







4. Measure the voltage between terminal 36 and ground.

OK: Battery positive voltage.

Q: Is the measured voltage battery voltage?

YES : Go to Step 7.

NO : Go to Step 6.

STEP 6. Check the wiring harness between audio amplifier connector D-29 (terminal 25, 35, 36) and fusible link (36).

- Check the power supply line for open circuit and short circuit.

NOTE: Also check intermediate connector C-47 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-47 is damaged, repair or replace the connector.

Q: Is the wiring harness between audio amplifier connector D-29 (terminal 25, 35, 36) and fusible link (36) in good condition?

YES : Go to Step 7.

NO : The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary.

STEP 7. Check radio and CD player connector C-109 and audio amplifier connector D-30 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are radio and CD player connector C-109 and audio amplifier D-30 in good condition?

YES : Go to Step 8.

NO : Repair or replace the damaged component(s).

STEP 8. Check the wiring harness between radio and CD player connector C-109 (terminal 17) and audio amplifier connector D-30 (terminal 3), and between radio and CD player connector C-109 (terminal 7) and audio amplifier connector D-29 (terminal 34).

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

NOTE: Also check intermediate connector C-24 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-24 is damaged, repair or replace the connector.

Q: Is the wiring harness between radio and CD player connector C-109 (terminal 17) and audio amplifier connector D-30 (terminal 3), and between radio and CD player connector C-109 (terminal 7) and audio amplifier connector D-29 (terminal 34)?

YES : Go to Step 9.

NO : The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary.

STEP 9. Retest the system

Replace the audio amplifier, then check that the audio sound is output.

Q: Is the check result normal?

YES : The trouble can be an intermittent malfunction.

NO : Replace the radio and CD player.