Inspection Procedure 5

INSPECTION PROCEDURE 5: On the Audio Screen, "COMMUNICATION ERROR" can not Proceed to Next Screen. (Middle Grade Type)







CIRCUIT OPERATION
The multi-center display unit (middle grade type) receives information from the radio, CD player and CD changer via M bus communication to display the audio system operation condition.

TECHNICAL DESCRIPTION (COMMENT)
The audio system operation screen will be frozen if the multi-center display (middle grade type) have received abnormal data from the radio, CD player and CD changer via M-bus communication within 30 seconds. If the abnormal data is received further 30 seconds from that point, a message "COMMUNICATION ERROR" will be displayed.

TROUBLESHOOTING HINTS
- Malfunction of multi-center display unit (middle grade type)
- Malfunction of radio, CD player and CD changer
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector.

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set

STEP 1. Check the communication condition by self-diagnostic function.







1. Start up the service mode to check the communication condition.

Q: Is "NG" displayed as the check results for M-bus communication?

YES : Go to Step 2.

NO : Go to Step 4.

STEP 2. Check radio, CD player and CD changer connector C-117 and multi-center display unit (middle grade type) connector C-05 for loose, corroded or damaged terminals, or terminals pushed back in the connector.







Q: Is radio, CD player and CD changer connector C-117 and multi-center display unit (middle grade type) connector C-05 in good condition?

YES : Go to Step 3.

NO : Repair or replace the component(s). Then go to step 1.

STEP 3. Check the wiring harness between radio, CD player and CD changer connector C-117 (terminal 26, 22, 21 and 27) and multi-center display unit (middle grade type) connector C-05 (terminal 7, 9, 8 and 10).







- Check the wiring harness for open circuit and short circuit.

Q: Is the wiring harness between radio, CD player and CD changer connector C-117 (terminal 26, 22, 21 and 27) and multi-center display unit (middle grade type) connector C-05 (terminal 7, 9, 8 and 10) in good condition?

YES : Go to Step 4.

NO : Repair the wiring harness and then go to step 1.

STEP 4.Using the oscilloscope, check the M BUS line.

1. Connect the multi-center display unit (middle grade type) connector C-05 and radio, CD player and CD changer connector C-117.







2. Connect the oscilloscope probe to terminal 10 of the multi-center display unit (middle grade type) connector by backprobing.
3. Turn the ignition switch to "ACC" position.
4. Operate each of the radio, CD player and CD changer switches.

Q: Is a wave pattern displayed?

YES : Intermittent malfunction.

NO : Replace multi-center display unit (middle grade type) and then go to Step 5.

STEP 5. Retest the system

Confirm that the audio operation screen is displayed normally.

Q: Is the check result satisfactory?

YES : The procedure is complete.

NO : Replace radio, CD player and CD changer and then go to step 6.

STEP 6. Retest the system

Confirm that the audio operation screen is displayed normally.

Q: Is the check result satisfactory?

YES : The procedure is complete.

NO : Go to step 1.