Inspection Procedure 12: Communication with M.U.T.-III is not Possible.

caution

Before replacing the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit are normal.

COMMENTS ON TROUBLE SYMPTOM

When scan tool MB991958 cannot communicate with the MMCS (audio visual navigation unit), the CAN bus line, CAN box unit power supply circuit system, audio visual navigation unit or, or CAN box unit may be faulty.

PROBABLE CAUSES

Damaged wiring harness and connectors
Malfunction of audio visual navigation unit
Malfunction of CAN box unit
Wrong routing of scan tool harness
Abnormality in power supply voltage to CAN box unit
ECU malfunction of other system

DIAGNOSIS PROCEDURE

STEP 1. Perform "Network/Connect Line Check" of the MMCS service mode.

Perform "Network/Connect Line Check" of the MMCS service mode, and check that the communication between the CAN box unit and the audio visual navigation unit is normal (Refer to

note

When the communication between the CAN box unit and the audio visual navigation unit is normal, "CAN BOX" is displayed on the check result screen. However, if the communication is not possible, "CAN BOX" is not displayed.

Q. Is "CAN BOX" displayed?

	Go to Step 2.

	Go to Step 3.

STEP 2. M.U.T.-III CAN bus diagnostics.

Use the M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?

	The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).

	Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ).

STEP 3. Connector check: C-15 CAN box unit connector and C-08 audio visual navigation unit connector

Q. Is the check result normal?

	Go to Step 4.

	Repair or replace the damaged component(s).

STEP 4. Check the wiring harness between C-15 CAN box unit connector terminal No.4, 5, 6 and C-08 audio visual navigation unit connector terminal No.59, 43, 58.

Q. Is the check result normal?

	Go to Step 5.

	Repair the wiring harness.

STEP 5. Substitute a known good CAN box unit, and check the trouble symptom.

Check whether scan tool MB991958 with CAN box unit normally.

Q. Is the check result normal?

	Replace the CAN box unit.

	Replace the audio visual navigation unit.