Inspection Procedure 12

Inspection Procedure 12: Communication with scan tool is not possible.

CAN Box Unit Communication Circuit:

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
- Audio visual navigation unit malfunction
- CAN box unit malfunction
- Wrong routing of scan tool harness
- Abnormality in power supply voltage to CAN box unit
- ECU malfunction of other system

DIAGNOSIS

Required Special Tools:
- 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 (Vehicles with CAN communication system)

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.

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?

YES: Go to Step 2.

NO: Go to Step 3.




STEP 2. Using scan tool MB991958, diagnose the CAN bus line.

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

1. Connect scan tool MB991958. Refer to Body Control Systems, ETACS, Diagnosis, "How to connect the Scan Tool (M.U.T.- III)."
2. Turn the ignition switch to the "ON" position.
3. Diagnose the CAN bus line.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the CAN bus line found to be normal?

YES: Intermittent malfunction is suspected. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.

NO: Repair the CAN bus line. (Refer to Information Bus, Diagnosis).

STEP 3. Check CAN box unit connector C-13 and audio visual navigation unit connector C-07 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are CAN box unit connector C-13 and audio visual navigation unit connector C-07 in good condition?

YES: Go to Step 4.

NO: Repair or replace the damaged component(s). Refer to Harness Connector Inspection. The steering remote control switch should work normally.

STEP 4. Check the wiring harness between CAN box unit connector C-13 (terminal 4, 5, 6) and audio visual navigation unit connector C-07 (terminal 43, 59, 58).

Q: Is the wiring harness between CAN box unit connector C-13 (terminal 4, 5, 6) and audio visual navigation unit connector C-07 (terminal 43, 59, 58) in good condition?

YES: Go to Step 5.

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. 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?

YES: Replace the CAN box unit.

NO: Replace the audio visual navigation unit.