Inspection Procedure 1

Inspection Procedure 1: Scan tool MB991958 cannot Communicate with the Electronic Control AWD System.

















COMMENTS ON TROUBLE SYMPTOM

If scan tool MB991958 cannot communicate with the electronic control AWD system, the CAN bus lines may have a problem. If the electronic control AWD system is not in operation (in case of no AWD operation), the AWD-ECU power supply circuit system or AWD-ECU may have a problem.

TROUBLESHOOTING HINTS

- Damaged wiring harness and connectors

- AWD-ECU malfunction

DIAGNOSIS

Required Special Tools:

- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface

- MB991827: M.U.T.-III USB Cable

- MB991910: M.U.T.-III Main Harness A

STEP 1. Scan tool MB991958 CAN bus diagnostics

Use scan tool MB991958 to diagnose the CAN bus lines.

Q. Is the check result normal?

YES Go to Step 2.
NO Repair the CAN bus line CAN Bus Diagnostics Chart). On completion, go to Step 2.
STEP 2. Check the following connector:

Check the connectors below for improper engagement, terminal damage or terminal drawn in the connector case.

- C-57 AWD-ECU connector

- C-309, C-313 ETACS-ECU connector

- D-52 joint connector (2)

Q. Are the connectors and terminals in good condition?

YES Go to Step 3.
NO Repair the connector(s) or terminal(s). Then go to Step 8.
STEP 3. Voltage measurement at the AWD-ECU connector

(1)Disconnect the C-57 AWD-ECU connector.

(2)Turn the ignition switch to the ON position.

(3)Measure the voltage between the C-57 wiring harness side connector terminals No.3, No.4 (Ignition switch "ON") and the body ground.
OK: System voltage


Q. Is the check result normal?

YES Go to Step 5.
NO Go to Step 4.
STEP 4. Wiring harness check

Check the wiring harness between the C-57 AWD-ECU connector (terminal No.4) and the C-313 ETACS-ECU connector (terminal No.2) for damage or other problem.

Q. Is the wiring harness in good condition?

YES Go to Step 7.
NO Repair the wiring harness. Then go to Step 8.
STEP 5. Resistance measurement at the AWD-ECU connector

(1)Disconnect the C-57 AWD-ECU connector.

(2)Measure the resistance between the C-57 wiring harness side connector terminals No. 10 and the body ground.
OK: Continuity exists (2 ohms or less)


Q. Is the check result normal?

YES Go to Step 7.
NO Go to Step 6.
STEP 6. Wiring harness check

Check the wiring harness between the C-57 AWD-ECU connector (terminal No.10) and the body ground for damage or other problem.

Q. Is the wiring harness in good condition?

YES Go to Step 7.
NO Repair the wiring harness. Then go to Step 8.
STEP 7. Retest the system.

Q. Does the malfunction occur again?

YES Replace AWD-ECU (Refer to Electronic Control AWD). Then go to Step 8.
NO The trouble can be an intermittent malfunction How to Cope With Intermittent Malfunctions).
STEP 8. Retest the system.

Q. Does the malfunction occur again?

YES Diagnose again from Step 1.
NO The procedure is complete.