Code No.03 Communication Error with Front-ECU




















caution If diagnosis code No.03 is set in the ETACS-ECU, diagnose the CAN bus lines.
note When the diagnosis codes relating to the CAN communication error are set, make sure of the vehicle equipment. When the vehicle is not equipped with the system the SWS communicates to, the diagnosis code is always set. This is not abnormal.

TROUBLE JUDGMENT
The ETACS-ECU communicates with the front-ECU through the SWS communication line. If there is any trouble in that communication, diagnosis code No.03 will be set.

COMMENTS ON TROUBLE SYMPTOM
The front-ECU, the ETACS-ECU, connector(s), or wiring harness between the two may be defective.

PROBABLE CAUSES

  • Malfunction of the front-ECU
  • Malfunction of the ETACS-ECU
  • Damaged harness wires and connectors

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54D - Troubleshooting ).

STEP 2. M.U.T.-III diagnosis code
(1)Erase the diagnosis code.
(2)Ignition switch: LOCK (OFF) position to ON
(3)On completion, check that diagnosis code No.03 is not reset.

Q. Is diagnosis code No.03 set?
Go to Step 3.
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use troubleshooting/Inspection Service Points ).

STEP 3. Connector check: A-08X front-ECU connector

Q. Is the check result normal?
Go to Step 4.
Repair the defective connector.

STEP 4. Voltage measurement at A-08X front-ECU connector.
(1)Remove the front-ECU, and measure at the relay box side.
(2)Voltage between A-08X front-ECU connector terminal No.7 and body earth
OK: System voltage

Q. Is the check result normal?
Go to Step 6.
Go to Step 5.

STEP 5. Check the wiring harness between A-08X front-ECU connector terminal No.7 and the fusible link (1).

  • Check the power supply line for open circuit.

Q. Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use troubleshooting/Inspection Service Points ).
Repair the wiring harness.

STEP 6. Connector check: A-09X front-ECU connector

Q. Is the check result normal?
Go to Step 7.
Repair the defective connector.

STEP 7. Voltage measurement at A-09X front-ECU connector.
(1)Remove the front-ECU, and measure at the relay box side.
(2)Turn the ignition switch to the ON position.
(3)Voltage between A-09X front-ECU connector terminal No.30 and body earth
OK: System voltage

Q. Is the check result normal?
Go to Step 9.
Go to Step 8.

STEP 8. Check the wiring harness between A-09X front-ECU connector terminal No.30 and the ignition switch (IG2).
note Prior to the wiring harness inspection, check joint connector D-37, intermediate connector D-241, junction block connectors D-401 and D-403, A/C condenser fan relay or no connection connector A-10X, and repair if necessary.

  • Check the power supply line for open circuit.

Q. Is the check result normal?
Refer to GROUP 54A - Ignition switch .
Repair the wiring harness.

STEP 9. Resistance measurement at A-09X front-ECU connector.
(1)Remove the front-ECU, and measure at the relay box side.
(2)Resistance between A-09X front-ECU connector terminal No.31 and body earth
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?
Go to Step 11.
Go to Step 10.

STEP 10. Check the wiring harness between A-09X front-ECU connector terminal No.31 and the body earth.

  • Check the earth wires for open circuit.

Q. Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use troubleshooting/Inspection Service Points ).
Repair the wiring harness.

STEP 11. Connector check: D-420 ETACS-ECU connector

Q. Is the check result normal?
Go to Step 12.
Repair the defective connector.

STEP 12. Check the wiring harness between D-420 ETACS-ECU connector terminal No.59 and A-09X front-ECU connector terminal No.22.
note Prior to the wiring harness inspection, check intermediate connector D-241, and repair if necessary.

  • Check the communication lines for open and short circuit.

Q. Is the check result normal?
Go to Step 13.
Repair the wiring harness.

STEP 13. Check whether the diagnosis code is reset.
Replace the front-ECU, and then check that the diagnosis code is not reset to the ETACS-ECU.
(1)Replace the front-ECU.
(2)Erase the diagnosis code.
(3)Ignition switch: LOCK (OFF) position to ON
(4)On completion, check that diagnosis code No.03 is not reset.

Q. Is diagnosis code No.03 set?
Replace the ETACS-ECU.
The procedure is complete.