Inspection Procedure 3: AWC-ECU Power Supply Circuit Malfunction (Control Mode Is Not Displayed.)

INSPECTION PROCEDURE 3: AWC-ECU power supply circuit malfunction (Control mode is not displayed.)





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
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. (Refer to How to Cope with Intermittent Malfunction).
NO: Go to Step 3.

STEP 3. Voltage measurement at C-51 AWC-ECU connector
Disconnect the connector, and measure the voltage between terminal No. 12 and ground at the wiring harness side.
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: C51, 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-51 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 C35 intermediate connector. When no problem is found, repair the wiring harness. Then go to Step 13.

STEP 6. Voltage measurement at C-51 AWC-ECU connector
1) Disconnect the connector, and measure the voltage between terminal No. 16 and ground at the wiring harness side.
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: C51, 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-51 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: When no problem is found, repair the wiring harness. Then go to Step 11.

STEP 9. AWC-ECU connector check: C-51

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-51 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 data list
Item No.43: Battery voltage.

Q: Is the check result normal?
YES: Intermittent malfunction. (Refer to How to Cope with Intermittent Malfunction).
NO: Replace the AWC-ECU. Then go to Step 13.

STEP 12. Retest the system.

Q: Is the check result normal?
YES: Intermittent malfunction. (Refer to How to Cope with Intermittent Malfunction)
NO: Replace the ETACS-ECU. Then go to Step 13.

STEP 13. Retest the system.

Q: Is the check result normal?
YES: Return to Step 1.
NO: This diagnosis is complete.