Inspection Procedure 1: Communication with Engine-ECU is Not Possible
OPERATION
- Battery voltage is applied to the diagnosis connector terminal.
- The diagnosis connector terminal is earthed 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 earthing circuit are defective. Communication cannot be achieved either, if a wrong vehicle type is selected on M.U.T.-III.
PROBABLE CAUSES
- 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
|
|
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 10.
|
|
|
|
|
|
 Go to Step 2.
|
|
|
|
|
|
STEP 2. Check battery voltage.
|
|
|
- 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. Voltage measurement at diagnosis connector (power supply line).
|
|
|
(1)Check the voltage between the diagnosis connector (power supply line) and body earth.
OK: System voltage
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 6.
|
|
|
|
|
|
Go to Step 4.
|
|
|
|
|
|
STEP 4. Check of short to earth, and open circuit in MUT line between ETACS-ECU connector and diagnosis connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 5.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 5. Check of short to earth, and open circuit in +B1 line between battery and ETACS-ECU connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Check fuse in the ETACS-ECU, and replace if necessary. If the fuse is normal, replace the ETACS-ECU.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 6. Resistance measurement at diagnosis connector (body earth line).
|
|
|
(1)Check the resistance between the diagnosis connector (body earth line) and body earth.
OK: Continuity (2 Ω or less)
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 7.
|
|
|
|
|
|
Repair or replace the connector(s), or check and repair the harness of open circuit and damage in power supply line between diagnosis connector and body earth
|
|
|
|
|
|
STEP 7. Continuity check on ETACS-ECU connectors
|
|
|
(1)Disconnect the connector, and measure at the ETACS-ECU side.
|
|
|
(2)Continuity check between the ETACS-ECU connector (+B1 terminal) and the ETACS-ECU connector (MUT terminal).
OK: Continuity
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 8.
|
|
|
|
|
|
Check fuse in the ETACS-ECU, and replace if necessary. If the fuse is normal, replace the ETACS-ECU.
|
|
|
|
|
|
STEP 8. Check of harness damage in +B1 line between battery and ETACS-ECU connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Go to Step 9.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 9. Check of harness damage in MUT line between ETACS-ECU connector and diagnosis connector.
|
|
|
Q.
Is the check result normal?
|
|
|
Refer to the M.U.T.-III reference manual.
|
|
|
|
|
|
Repair the connector(s) or wiring harness.
|
|
|
|
|
|
STEP 10. M.U.T.-III CAN bus diagnosis
|
|
|
- Use M.U.T.-III, perform CAN bus line diagnosis.
|
|
|
Q.
Is the check result normal?
|
|
|
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 ).
|
|
|
|