Inspection Procedure 3
INSPECTION PROCEDURE 3: AWC-ECU power supply circuit malfunction
POWER SUPPLY SYSTEM CIRCUIT
Refer to C2100.
CAUTION:
- If there is any problem in the CAN bus lines, an incorrect trouble symptom may occur. Prior to this diagnosis, always diagnose the CAN bus lines.
- Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
COMMENTS ON TROUBLE SYMPTOM
If the S-AWC system does not work, or does not communicate with the scan tool, AWC-ECU power supply circuit, ground circuit, or AWC-ECU may have a problem.
PROBABLE CAUSES
- Malfunction of the ETACS-ECU
- Damaged harness wires and connectors
- Malfunction of AWC-ECU
DIAGNOSTIC PROCEDURE
STEP 1. Scan tool CAN bus diagnostics
Using scan tool MB991958, diagnose the CAN bus lines.
Q. Is the check result normal?
YES Go to Step 3.
NO Repair the CAN bus lines. CAN Bus Diagnostics Chart.) After repairing the CAN bus line, go to Step 2.
STEP 2. Retest the system.
Q. Is the check result normal?
YES Intermittent malfunction. How to Cope With Intermittent Malfunctions.)
NO Go to Step 3.
STEP 3. Voltage measurement at C-46 AWC-ECU connector
Measure the voltage between C-46 AWC-ECU connector terminal No.12 - and the body ground.
OK: Battery positive voltage
Q. Is the check result normal?
YES Go to Step 6.
NO Go to Step 4.
STEP 4. AWC-ECU connector, ETACS-ECU connector check: C-46, C-315
Q. Is the check result normal?
YES Go to Step 5.
NO Repair the defective connector. Then go to Step 13.
STEP 5. Check the wiring harness between C-46 AWC-ECU connector terminal No. 12 and C-315 ETACS-ECU connector terminal No.4.
Check the wiring harness for open circuit.
Q. Is the check result normal?
YES Go to Step 12.
NO Check C-41 intermediate connector, C-103 J/C (3). When no problem is found, repair the wiring harness. Then go to Step 12.
STEP 6. Voltage measurement at C-46 AWC-ECU connector
(1)With C-46 AWC-ECU connector connected, measure the voltage between the terminal No. 16 and the body ground.
(2)Turn the ignition switch to the "ON" position.
OK: Battery positive voltage
Q. Is the check result normal?
YES Go to Step 9.
NO Go to Step 7.
STEP 7. AWC-ECU connector, ETACS-ECU connector check: C-46, C-313
Q. Is the check result normal?
YES Go to Step 8.
NO Repair the defective connector. Then go to Step 13.
STEP 8. Check the wiring harness between C-46 AWC-ECU connector terminal No. 16 and C-313 ETACS-ECU connector terminal No. 2.
Check the wiring harness for open circuit.
Q. Is the check result normal?
YES Go to Step 12.
NO Repair the wiring harness. Then go to Step 12.
STEP 9. AWC-ECU connector check: C-46
Q. Is the check result normal?
YES Go to Step 10.
NO Repair the defective connector. Then go to Step 13.
STEP 10. Check the wiring harness between C-46 AWC-ECU connector terminal No. 13 and body ground.
Check the wiring harness for open circuit.
Q. Is the check result normal?
YES Go to Step 11.
NO Repair the wiring harness. Then go to Step 13.
STEP 11. Scan tool service data
Item No. 43: Battery voltage (Refer to service data reference table Data List Reference Table.)
Q. Is the check result normal?
YES Intermittent malfunction. How to Cope With Intermittent Malfunctions.)
NO Replace the AWC-ECU.(Refer to Active Center Differential (ACD).) Then go to Step 13.
STEP 12. Retest the system.
Q. Is the check result normal?
YES Replace the ETACS-ECU. Electronic Time and Alarm Control System (ETACS)-ECU Removal and Installation.) Then go to Step 13.
NO Intermittent malfunction. How to Cope With Intermittent Malfunctions.)
STEP 13. Retest the system.
Q. Is the check result normal?
YES Return to Step 1.
NO This diagnosis is complete.