Inspection Procedure 3: AWC-ECU Power Supply Circuit Malfunction
INSPECTION PROCEDURE 3: AWC-ECU power supply circuit malfunctionPOWER SUPPLY SYSTEM CIRCUIT
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. After repairing the CAN bus line, go to Step 2.
STEP 2. Retest the system.
Q: Is the check result normal?
YES: Intermittent malfunction.
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 C41 intermediate connector, C-43 J/C (4), 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: Check D-27 J/C (5). When no problem is found, 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 (Data List Reference Table)
Q: Is the check result normal?
YES: Intermittent malfunction.
NO: Replace the AWC-ECU. Then go to Step 13.
STEP 12. Retest the system.
Q: Is the check result normal?
YES: Replace the ETACS-ECU. Then go to Step 13.
NO: Intermittent malfunction.
STEP 13. Retest the system.
Q: Is the check result normal?
YES: Return to Step 1.
NO: This diagnosis is complete.