Inspection Procedure 2
Inspection Procedure 2: No sound is heard. [Vehicles with audio amplifier]CAUTION: Before replacing the radio and CD player or audio amplifier, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.
Audio System Circuit (Part 1):
Audio 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
- Malfunctions of radio and CD player
- Malfunction of audio amplifier
- 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. (Refer to Coding Table).
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-25 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is audio amplifier connector D-25 in good condition?
YES : Go to Step 3.
NO : Repair or replace the damaged component(s).
STEP 3. Check the ground circuit to the rear monitor.
Measure the resistance at audio amplifier connector D-25.
1. Disconnect audio amplifier connector D-25, 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-25 (terminal 24, 31, 32) and ground.
- Check the ground wires for open circuit.
Q: Is the wiring harness between audio amplifier connector D-25 (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 ETACS-ECU.
Measure the voltage at audio amplifier connector D-25.
1. Disconnect audio amplifier connector D-25, and measure the voltage available at the wiring harness-side connector.
2. Measure the voltage between terminal 25 and ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
3. Measure the voltage between terminal 35 and ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
4. Measure the voltage between terminal 36 and ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
Q: Is the measured voltage approximately 12 volts (battery positive voltage)?
YES : Go to Step 7.
NO : Go to Step 6.
STEP 6. Check the wiring harness between audio amplifier connector D-25 (terminal 25, 35, 36) and fusible link (36).
- Check the power supply lines for open circuit and short circuit.
Q: Is the wiring harness between audio amplifier connector D-25 (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-106 and audio amplifier connector D-26 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Are radio and CD player connector C-106 and audio amplifier D-26 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-106 (terminal 17) and audio amplifier connector D-26 (terminal 3)
- Check the communication line for open circuit and short circuit.
NOTE: Also check intermediate connector C-22 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-22 is damaged, repair or replace the connector as described.
Q: Is the wiring harness between radio and CD player connector C-106 (terminal 17) and audio amplifier connector D-26 (terminal 3) in good condition?
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. Check the wiring harness between radio and CD player connector C-106 (terminal 7) and audio amplifier connector D-25 (terminal 34)
- Check the communication line for open circuit and short circuit.
NOTE: Also check intermediate connector C-22 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-22 is damaged, repair or replace the connector as described.
Q: Is the wiring harness between radio and CD player connector C-106 (terminal 7) and audio amplifier connector D-25 (terminal 34) in good condition?
YES : Go to Step 10.
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 10. 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.