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

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 earthing circuit are defective. Communication cannot be achieved either, if a wrong vehicle type is selected on M.U.T.-III.

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

DIAGNOSIS PROCEDURE

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.

	Go to Step 6.

	Go to Step 2.

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

	Go to Step 3.

	Replace the battery.

(1)Check the voltage between the diagnosis connector (power supply line) and body earth.
OK: System voltage

	Go to Step 4.

	Repair or replace the connector(s), or check and repair the harness of open circuit, and short circuit in power supply line between diagnosis connector and battery.

(1)Check the resistance between the diagnosis connector (earth line) and body earth.
OK: Continuity (2 Ω or less)

	Go to Step 5.

	Repair or replace the connector(s), or check and repair the harness of open circuit, and damage in earth line between diagnosis connector and body earth.

	Go to Step 6.

	Repair the connector(s) or wiring harness.

	Check Inspection Procedure - engine-ECU power supply, engine control relay, ignition switch-IG1 system (Refer to ).

	Perform troubleshooting for CAN (Refer to GROUP 54C - Troubleshooting - CAN Bus Diagnostics Table ).