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). Refer to General (Electrical), Harness Connector Inspection. 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 26, 22, 21 and 27).






Q: Is the wiring harness between radio, CD player and CD changer connector C-117 (terminal 46, 42, 41 and 47) and multi-center display unit (middle grade type) connector C-05 (terminal 7, 8, 9 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 (Refer to General, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent malfunction.

NO : Replace multi-center display unit (middle grade type) and then go to Step 6.

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.