Inspection Procedure 1: Communication with Engine-ECU is Not Possible










OPERATION



  • Battery voltage is applied to the diagnosis connector (terminal No. 16).
  • The diagnosis connector (terminal No. 4 and No. 5) is grounded to the vehicle body.

COMMENTS ON TROUBLE SYMPTOM



  • When the communication between M.U.T.-III and engine-ECU is impossible, it can be suspected that the CAN bus line, power supply circuit of the diagnosis connector, and/or grounding circuit are defective.Communication can not be achieved either, if a wrong vehicle type is selected on M.U.T.-III.

PROBABLE CAUSES



  • Defective diagnosis connector.
  • Open/short circuit or harness damage in diagnosis connector circuit or loose connector contact.
  • Defective CAN communication.
  • Defective M.U.T.-III.
  • Failed engine-ECU

DIAGNOSIS PROCEDURE


STEP 1. Check the Vehicle Communication Interface (V.C.I.) operations



  • Connect the M.U.T.-III to the diagnosis connector.
  • When the power of Vehicle Communication Interface (V.C.I.) is turned to ON, the indicator lamp of the Vehicle Communication Interface (V.C.I.) illuminates in green.
OK: The indicator lamp of the Vehicle Communication Interface (V.C.I.) illuminates in green.

Q. Is the check result normal?

Go to Step 13 .
Go to Step 2 .

STEP 2. Check battery.



  • Check battery (Refer to GROUP 54A - Battery - On-vehicle Service - Battery Test ).

Q. Is the check result normal?

Go to Step 3 .
Replace the battery.

STEP 3. Connector check: C-127 diagnosis connector


Q. Is the check result normal?

Go to Step 4 .
Repair or replace the connector.

STEP 4. Perform voltage measurement at C-127 diagnosis connector.



  • Disconnect connector, and measure at harness side.
  • Voltage between terminal No. 16 and earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 8 .
Go to Step 5 .

STEP 5. Connector check: C-309 and C-317 ETACS-ECU connectors


Q. Are the check results normal?

Go to Step 6 .
Repair or replace the connector.

STEP 6. Continuity check on C-309 and C-317 ETACS-ECU connectors



  • Disconnect connectors, and measure at the ETACS-ECU side.
  • Continuity check between terminal No. 1 (C-309) and No. 8 (C-317)
OK: Continuity

Q. Is the check result normal?

Go to Step 7 .
Repair or replace the ETACS-ECU.

STEP 7. Check harness between the battery and C-309 (terminal No. 1) ETACS-ECU connector.



  • Check power supply line for open/short circuit.

Q. Is the check result normal?


    Check and repair the harness between C-317 (terminal No. 8) ETACS-ECU connector and C-127 (terminal No. 16) diagnosis connector.

    • Check power supply line for open/short circuit.
Repair the damaged harness wire.

STEP 8. Perform resistance measurement at C-127 diagnosis connector.



  • Pull out relay and measure at connector side.
  • Resistance between terminal No. 4, No. 5 and earth.
OK: Continuity (2 Ω or less)

Q. Is the check result normal?

Go to Step 9 .

    Check and repair the harness between the C-127 (terminal No. 4 or terminal No. 5) diagnosis connector and body earth.

    • Check earthing line for open circuit and damage.

STEP 9. Connector check: C-309 and C-317 ETACS-ECU connectors


Q. Is the check result normal?

Go to Step 10 .
Repair or replace the connector.

STEP 10. Continuity check on C-309 and C-317 ETACS-ECU connectors



  • Disconnect connectors, and measure at the ETACS-ECU side.
  • Continuity check between terminal No. 1 (C-309) and No. 8 (C-317)
OK: Continuity

Q. Is the check result normal?

Go to Step 11 .
Repair or replace the connector.

STEP 11. Check harness between the battery and C-309 (terminal No. 1) ETACS-ECU connector.



  • Check power supply line for damage.

Q. Is the check result normal?

Go to Step 12 .
Repair or replace the connector.

STEP 12. Check harness between C-317 (terminal No. 8) ETACS-ECU connector and C-127 (terminal No. 16) diagnosis connector.



  • Check power supply line for damage.

Q. Is the check result normal?

Refer to the M.U.T.-III reference manual.
Repair or replace the connector.

STEP 13. M.U.T.-III CAN bus diagnosis



  • Use M.U.T.-III, perform CAN bus line diagnosis.

Q. Is the check result normal?

Check engine-ECU power supply, engine control relay and ignition switch - IG1 system (Refer to Inspection Procedure 3 ).
Perform troubleshooting for CAN (Refer to GROUP 54C - Troubleshooting - CAN Bus Diagnostics Table ).