INSPECTION PROCEDURE 3: Transfer-ECU Power Supply Circuit Malfunction


POWER SUPPLY SYSTEM CIRCUIT



caution
  • If there is any problem in the CAN bus lines, an incorrect trouble symptom may occur. Prior to this diagnosis, always diagnose the CAN bus lines.
  • Whenever the ECU is replaced, ensure that the CAN bus lines are normal.

SYMPTOMS



PROBABLE CAUSES



  • Damaged harness wires and connectors
  • Malfunction of transfer-ECU

DIAGNOSIS PROCEDURE

STEP 1. Measure the voltage at transfer-ECU connector D-124.
(1)Disconnect the connector, and measure the voltage between terminal No.25 and earth at the wiring harness side.
(2)Turn the ignition switch to the ON position.
OK: System voltage

Q. Is the check result normal?
Go to Step 4.
Go to Step 2.

STEP 2. Connector check: D-309 ignition switch connector, D-401, D-403 J/B connector, D-225, D-229 intermediate connector, D-124 transfer-ECU connector.
Check for the contact with terminals.

Q. Is the check result normal
Go to Step 3.
Repair the defective connector.

STEP 3. Check the harness between ignition switch connector D-309 terminal No.2 and transfer-ECU connector D-124 terminal No.25.
Check the power supply line for short or open circuit.

Q. Is the check result normal?
Check the ignition switch system (Refer to GROUP 54A - Ignition Switch, Troubleshooting ).
Repair the wiring harness.

STEP 4. Measure the resistance at transfer-ECU connector D-124.
Disconnect the connector, and measure the resistance between terminal No.10, 11 and earth at the wiring harness side.
OK: Continuity (2 Ω or less)

Q. Is the check result normal?
Go to Step 7.
Go to Step 5.

STEP 5. Connector check: D-124 transfer-ECU connector.
Check for the contact with terminals.

Q. Is the check result normal?
Go to Step 6.
Repair the defective connector.

STEP 6. Check the harness between transfer-ECU connector D-124 terminal No.10, 11 and earth.
Check the earth line for open circuit.

Q. Is the check result normal?
Go to Step 7.
Repair the wiring harness.

STEP 7. Retest the system.

Q. Is the check result normal?
Intermittent malfunction. (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)
Replace the transfer-ECU.