Inspection Procedure 4

INSPECTION PROCEDURE 4: On the Audio Screen, "E" cannot Proceed to Next Screen.

M-BUS Line Circuit:

CIRCUIT OPERATION
The multi-center display unit receives information from the radio and CD player with CD changer or radio and CD player 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 have received abnormal data from the radio and CD player with CD changer or radio and CD player via M-bus communication within 30 seconds. If the abnormal data is received further 30 seconds from that point, a message "E" will be displayed.

TROUBLESHOOTING HINTS
- Malfunction of multi-center display unit
- Malfunction of radio and CD player with CD changer or radio and CD player
- 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
- MB992006: Extra Fine Probe

STEP 1. Check of the display.

Q: Is "E" displayed?

YES: Go to Step 2.

NO: Go to Step 4.

STEP 2. Check radio and CD player with CD changer connector C-119 or radio and CD player connector C-118 and multi-center display unit connector C-06 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is radio and CD player with CD changer connector C-119 or radio and CD player connector C-118 and multi-center display unit connector C-06 in good condition?

YES: Go to Step 3.

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

STEP 3. Check the wiring harness between radio and CD player with CD changer connector C-119 (terminal 27, 28, 38 and 39) or radio and CD player connector C-118 (terminal 21, 22, 26 and 27) and multi-center display unit connector C-06 (terminal 7, 8, 9 and 10).

Q: Is the wiring harness between radio and CD player with CD changer connector C-119 (terminal 27, 28, 38 and 39) or radio and CD player connector C-118 (terminal 21, 22, 26 and 27) and multi-center display unit connector C-06 (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 connector C-06 and radio and CD player with CD changer connector C-119 or radio and CD player connector C-118 .
2. Connect the oscilloscope probe to terminal 10 of the multi-center display unit connector by backprobing.
3. Turn the ignition switch to ACC position.
4. Operate each of the radio and CD player with CD changer switches or radio and CD player switches.

Q: Is a wave pattern displayed?

YES: Go to Step 5.

NO: Replace multi-center display unit 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: Intermittent malfunction (Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent malfunction.

NO: Replace radio and CD player with CD changer or radio and CD player 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.