Inspection Procedure 1: Communication with engine-ECU <M/T> or engine-A/T-ECU <A/T> is not possible.

OPERATION

The battery voltage is applied to the diagnosis connector (terminal No. 16) and is earthed to the vehicle body from the diagnosis connector (terminal No. 4 and No. 5).

COMMENT ON TROUBLE SYMPTOM

If the M.U.T.-III cannot communicate with the engine-ECU <M/T> or engine-A/T-ECU <A/T> system, the CAN bus lines may be defective. If the engine-ECU <M/T> or engine-A/T-ECU <A/T> system dose not work, the engine-ECU <M/T> or engine-A/T-ECU <A/T> or its power supply circuit may be defective. This symptom also appears when an incorrect vehicle model is selected on the M.U.T.-III.

PROBABLE CAUSES

Open/short circuit in diagnosis connector circuit or loose connector contact
Failed CAN
Failed M.U.T.-III
Failed engine-ECU <M/T> or engine-A/T-ECU <A/T>

DIAGNOSIS PROCEDURE

STEP 1. Check engine start-up.

Connect the M.U.T.-III to the diagnosis connector.
Ignition switch: ON
When the V.C.I. is energised, the V.C.I. indicator lamp should be illuminate in a green colour.

OK: The V.C.I. is indicator lamp illuminates in a green colour.

Q. Is the check result normal?

	Go to Step 6 .

	Go to Step 2 .

STEP 2. Check battery voltage.

Measure battery voltage during cranking.

OK: 8 V or more

Q. Is the check result normal?

	Go to Step 3 .

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

STEP 3. Connector check: D-127 diagnosis connector

Q. Is the check result normal?

	Go to Step 4 .

	Repair or replace the connector.

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

Voltage between terminal No. 16 and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 5 .

	Check intermediate connectors D-240, D-404 and 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. Check power supply line for open/short circuit.

STEP 5. Perform resistance measurement at D-127 diagnosis connector.

Resistance between terminal No. 4 and earth, also between terminal No. 5 and earth.

OK: Continuity (2 Ω or less)

Q. Is the check result normal?

	Refer to M.U.T.-III Reference Manual - Troubleshooting Procedures.

	Check and repair harness between diagnosis connector and body earth. Check and repair harness between D-127 (terminal No. 4) diagnosis connector and body earth. Check and repair harness between D-127 (terminal No. 5) diagnosis connector and body earth. Check earthing line for open circuit and damage

STEP 6. M.U.T.-III CAN bus diagnosis

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

Q. Is the check result normal?

	Check engine-ECU <M/T> or engine-A/T-ECU <A/T> power supply, engine control relay and ignition switch IG1 system (Refer to Inspection Procedure 20 ).

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