Inspection Procedure A-2: Communication with the M.U.T.-III 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 ETACS-ECU is defective, or the wiring harness between the diagnosis connector and the ETACS-ECU or their connector(s) is damaged.
note If the wiring harness between the ETACS-ECU and body earth is defective, also check D-419 ETACS-ECU connector terminal No.3, and repair if necessary.

PROBABLE CAUSES

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

DIAGNOSIS PROCEDURE

STEP 1. Check that the M.U.T.-III communicates with the other systems.
Use the M.U.T.-III to confirm that it communicates with the engine-ECU.

Q. Is the check result normal?
Go to Step 2.
Diagnose the system, which cannot communicate with the M.U.T.-III.

STEP 2. Check that the M.U.T.-III can communicate with the system.
When the ignition switch is turned ON, check if the M.U.T.-III can communicate with the system.

Q. Is the check result normal?
Refer to inspection procedure A-1 "Check the battery power supply circuit to the ETACS-ECU ."
Go to Step 3.

STEP 3. Connector check: D-420 ETACS-ECU connector

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

STEP 4. Resistance measurement at the D-420 ETACS-ECU connector.
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Resistance between D-420 ETACS-ECU connector terminal No.56 and body earth
OK: Continuity exists (2 Ω or less)

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

STEP 5. Check the wiring harness between D-420 ETACS-ECU connector terminal No.56 and body earth.

  • Check the earth wires for open circuit.

Q. Are the check results 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: D-127 diagnosis connector

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

STEP 7. Check the wiring harness from D-420 ETACS-ECU connector terminal Nos.51, 59 and 67 to D-127 diagnosis connector terminal Nos.9, 3 and 1.
note Prior to the wiring harness inspection, check joint connector D-34, and repair if necessary.

  • Check the communication lines for open circuit.

Q. Are the check results normal?
Go to Step 8.
Repair the wiring harness.

STEP 8. Retest the system.
Check whether the communication with the M.U.T.-III is possible.

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