Inspection Procedure 1: Communication with engine-ECU is not possible








OPERATION



  • The M.U.T.-III receives data from the engine-ECU via the CAN bus line.

PROBABLE CAUSES



  • Damaged connector (Engine-ECU connector, diagnosis connector)
  • Damaged harness (Open or short circuit in the engine-ECU power supply circuit, open circuit between diagnosis connector and battery, and open circuit between diagnosis connector and earth)
  • Failed CAN bus line
  • Failed M.U.T.-III
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check the V.C.I. indicator lamp illuminates.



  • Connect the M.U.T.-III to the diagnosis connector.

Q. Is the V.C.I. indicator lamp illuminates in a green colour?

CAN bus diagnosis (Refer to GROUP 54D - Troubleshooting - Can Bus Diagnosis Table ).

Go to Step 2 .

STEP 2. Connector check: D-127 diagnosis connector

Q. Is the check result normal?
Go to Step 3 .
Repair or replace.

STEP 3. Perform voltage measurement for open circuit at D-127 diagnosis connector.

  • Voltage between terminal No. 16 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 4 .
Check intermediate connectors D-404, D-405, and repair if necessary. If intermediate connectors are normal, check and repair harness between D-127 (terminal No. 16) diagnosis connector and battery.

STEP 4. Check for open circuit between D-127 diagnosis connector and earth.

  • Disconnect connector.
  • Check open circuit between terminal No. 4 and earth also between terminal No. 5 and earth.

Q. Is the check result normal?
Refer to M.U.T.-III User’s Manual - Troubleshooting Procedures.
Repair harness between diagnosis connector and body earth.