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 J/B connector, 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.

	Repair harness between D-127 (terminal No. 16) diagnosis connector and D-405 (terminal No. 12) J/B connector.

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.