INSPECTION PROCEDURE A-4: Communication with the front-ECU is not possible.


caution Whenever the ECU is replaced, ensure that the power supply circuit, the earthing circuit and the communication circuit are normal.


COMMENTS ON TROUBLE SYMPTOM
It is suspected that the power supply circuit to the front-ECU is defective, or the wiring harness between the SWS monitor and the front-ECU or their connector(s) is damaged. If the battery power supply circuit to the ECU (terminal No.7 of the front-ECU) is damaged, also check the power supply circuit from the ignition switch (IG2) (terminal No.30 of the front-ECU), and repair if necessary.

POSSIBLE CAUSES

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

DIAGNOSIS PROCEDURE

Step 1. ECU check by using the SWS monitor
Check that the power supply and earth lines to the ETACS-ECU and the SWS communication lines are normal.

  • Ignition switch: OFF
ECUS TO BE CHECKED
  • ETACS ECU
OK: "OK" is displayed on the "ETACS ECU" menu.

Q. Is the check result normal?
Go to Step 2.
Refer to Inspection Procedure A-3 "Communication with ETACS-ECU is not possible ."

Step 2. Connector check: A-14X front-ECU connector

Q. Is the check result normal?

Go to Step 3.

Repair the defective connector.

Step 3. Voltage measurement at A-14X front-ECU connector.

(1)Disconnect the connector, and measure at the relay box side.

(2)Voltage between A-14X front-ECU connector No.7 and body earth
OK: System voltage

Q. Is the check result normal?

Go to Step 5.

Go to Step 4.

Step 4. Check the wiring harness between A-14X front-ECU connector terminal No.7 and the fusible link (26).


  • 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 Cope with Intermittent Malfunction ).

Repair the wiring harness.

Step 5. Connector check: A-15X front-ECU connector

Q. Is the check result normal?

Go to Step 6.

Repair the defective connector.

Step 6. Resistance measurement at A-15X front-ECU connector.

(1)Disconnect the connector, and measure at the relay box side.

(2)Resistance between A-15X front-ECU connector terminal No.31 and body earth
OK: 2 Ω or less

Q. Is the check result normal?

Go to Step 9.

Go to Step 7.

Step 7. Connector check: A-25 earth connector


Q. Is the check result normal?

Go to Step 8.

Repair the defective connector.

Step 8. Check the wiring harness between A-15X front-ECU terminal connector terminal No.31 and A-25 earth connector terminal No.5.




  • 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 Cope with Intermittent Malfunction ).

Repair the wiring harness.

Step 9. Connector check: C-221 ETACS-ECU connector


Q. Is the check result normal?

Go to Step 10.

Repair the defective connector.

Step 10. Check the wiring harness between A-15X front-ECU connector terminal No.22 and C-221 ETACS-ECU connector terminal No.59.






note Prior to the wiring harness inspection, check joint connector C-01 and intermediate connector C-125, and repair if necessary.

  • Check the communication lines for open circuit.

Q. Is the check result normal?

Go to Step 11.

Repair the wiring harness.

Step 11. ECU check by using the SWS monitor
Check that the power supply and earth lines to the front-ECU and the SWS communication lines are normal.

  • Ignition switch: ON
ECUS TO BE CHECKED
  • FRONT ECU
OK: "OK" is displayed on the "FRONT ECU" menu.

Q. Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
Replace the front-ECU.