Inspection Procedure 3: Engine-ECU Power Supply, Engine Control Relay, Ignition Switch-IG1 System












OPERATION



  • The battery voltage is applied to the engine control relay 1 (terminal No. 3 and No. 4).
  • The engine-ECU (terminal No. 42) makes the power transistor in the unit be in "ON" position and makes currents go on the engine control relay 1 coil, and that makes the relay be in "ON" position.
  • When the engine control relay 1 is in the "ON" position, the battery voltage is applied to engine-ECU, the terminal No. 35 and No. 47, from the engine control relay 1, terminal No. 2. At the same time, the battery voltage is applied to the relay coil of the engine control relay 2, the terminal No. 2.
  • When the engine control relay 2 is in "ON" position, the battery voltage is supplied to the engine-ECU (terminal No. 24, terminal No. 36 and terminal No. 48), the sensor and the actuator from the engine control relay (terminal No. 3).
  • The engine-ECU (terminal No. 11, terminal No. 12 and terminal No. 23) is earthing to the vehicle body.

FUNCTION



  • When the ignition switch ON signal is input to the engine-ECU, the engine-ECU places the engine control relay in the "ON" position. Accordingly, the battery voltage is supplied to the engine-ECU, sensor and actuator.

PROBABLE CAUSES



  • Failed engine control relay
  • Open/short circuit or harness damage in engine control relay circuit or loose connector contact.
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check battery.

  • Check battery (Refer to GROUP 54A - Battery - On-vehicle Service - Battery test ).

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

STEP 2. Connector check: C-317 and C-304 ETACS-ECU connectors.

Q. Are the check results normal?
Go to Step 3 .
Repair or replace the connector.

STEP 3. Perform voltage measurement at C-317 ETACS-ECU connector.

  • Disconnect connector, and measure at the harness side.
  • Voltage between terminal No. 6 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 6 .
Go to Step 4 .

STEP 4. Connector check: C-210 ignition switch connector

Q. Is the check result normal?
Go to Step 5 .
Repair or replace the connector.

STEP 5. Check ignition switch.

  • Check ignition switch (Refer to GROUP 54A - Ignition Switch - Inspection).

Q. Is the check result normal?

    Check and repair harness between C-210 (terminal No. 2) ignition switch connector and C-317 (terminal No. 6) ETACS-ECU connector.

    • Check output line for open/short circuit.
Replace the ignition switch.

STEP 6. Perform voltage measurement at B-18 engine-ECU connector.

  • Disconnect connector, and measure at the harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 34 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 8 .
Go to Step 7 .

STEP 7. Continuity check on C-304 and C-317 ETACS-ECU connectors.

  • Disconnect connectors, and measure at the ETACS-ECU side.
  • Continuity test between terminal No. 6 (C-317) and No. 10 (C-304).
note Connect the (+) side of circuit tester to terminal No. 10.
OK: Continuity

Q. Is the check result normal?

    Check and repair harness between C-304 (terminal No. 10) ETACS-ECU connector and B-18 (terminal No. 34) engine-ECU connector.

    • Check output line for open/short circuit.
Replace the ETACS-ECU.

STEP 8. Check harness between C-210 (terminal No. 2) ignition switch connector and C-317 (terminal No. 6) ETACS-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 9 .
Replace the ignition switch.

STEP 9. Check harness between C-304 (terminal No. 10) ETACS-ECU connector and B-18 (terminal No. 34) engine-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 10 .
Repair the damaged harness wire.

STEP 10. Connector check: A-33X engine control relay 1 connector.

Q. Is the check result normal?
Go to Step 11 .
Repair or replace the connector.

STEP 11. Check engine control relay 1.

  • Check engine control relay 1.

Q. Is the check result normal?
Go to Step 12 .
Replace the engine control relay 1.

STEP 12. Perform voltage measurement at A-33X engine control relay 1 connector.

  • Remove relay, and measure at the relay box side.
  • Voltage between terminal No. 3 and earth, also between terminal No. 4 and earth.
OK: System voltage

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

    Check and repair harness between battery and A-33X (terminal No. 3 and terminal No. 4) engine control relay 1 connector.

    • Check power supply line for open/short circuit.

STEP 13. Connector check: B-18 engine-ECU connector.

Q. Is the check result normal?
Go to Step 14 .
Repair or replace the connector.

STEP 14. Perform voltage measurement at B-18 engine-ECU connector.

  • Disconnect connector, and measure at the harness side.
  • Voltage between terminal No. 42 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 15 .

    Check and repair harness between A-33X (terminal No. 1) engine control relay 1 connector and B-18 (terminal No. 42) engine-ECU connector.

    • Check signal line for open/short circuit.

STEP 15. Connector check: A-21X engine control relay 2 connector.

Q. Is the check result normal?
Go to Step 16 .
Repair or replace the connector.

STEP 16. Check engine control relay 2.

  • Check engine control relay 2.

Q. Is the check result normal?
Go to Step 17 .
Replace the engine control relay 2.

STEP 17. Perform voltage measurement at A-21X engine control relay 2 connector.

  • Remove relay, and measure at the relay box side.
  • Ignition switch: ON
  • Voltage between terminal No. 2 and earth, also between terminal No. 4 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 21 .
Go to Step 18 .

STEP 18. Check harness between A-33X (terminal No. 2) engine control relay 1 connector and A-21X (terminal No. 2 and terminal No. 4) engine control relay 2 connector.

  • Check output line for open/short circuit.

Q. Is the check result normal?
Go to Step 19 .
Repair the damaged harness wire.

STEP 19. Check harness between battery and A-33X (terminal No. 3 and terminal No. 4) engine control relay 1 connector.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 20 .
Repair the damaged harness wire.

STEP 20. Check harness between A-33X (terminal No. 1) engine control relay 1 connector and B-18 (terminal No.42) engine-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Replace the engine-ECU.
Repair the damaged harness wire.

STEP 21. Perform resistance measurement at A-21X engine control relay 2 connector.

  • Disconnect connector, and measure at the harness side.
  • Resistance between terminal No. 1 and earth.
OK: Continuity (2 Ω or less)

Q. Is the check result normal?
Go to Step 22 .

    Check and repair harness between A-21X (terminal No. 1) engine control relay 2 connector and body earth.

    • Check earthing line for open circuit or damage.

STEP 22. Perform voltage measurement at B-18 engine-ECU connector.

  • Disconnect connector, and measure at the harness side.
  • Using a jumper wire, connect terminal No. 42 to earth.
  • Voltage between terminal No. 23 and earth, between terminal No. 36 and earth, also between terminal No. 48 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 24 .
Go to Step 23 .

STEP 23. Check harness between A-21X (terminal No. 3) engine control relay 2 connector and B-18 (terminal No. 24, terminal No. 36 and terminal No. 48) engine-ECU connector.

  • Check output line for open/short circuit.

Q. Is the check result normal?

    Check and repair harness between A-33X (terminal No. 2) engine control relay 1 connector and A-21X (terminal No. 2 and terminal No. 4) engine control relay 2 connector.

    • Check output line for damage.
Repair the damaged harness wire.

STEP 24. Perform voltage measurement at B-18 engine-ECU connector.

  • Disconnect connector, and measure at the harness side
  • Using a jumper wire, connect terminal No. 42 to earth.
  • Voltage between terminal No. 23 and earth, between terminal No. 36 and earth also between terminal No. 35 and earth, also between terminal No. 47 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 25 .

    Check and repair harness between A-33X (terminal No. 2) engine control relay 1 connector and B-18 (terminal No. 35 and terminal No. 47) engine-ECU connector.

    • Check output line for damage.

STEP 25. Perform resistance measurement at B-18 engine-ECU connector.

  • Disconnect connector, and measure at the harness side.
  • Resistance between terminal No. 11 and earth, between terminal No. 12 and earth, also between terminal No. 23 and earth.
OK: Continuity (2 Ω or less)

Q. Is the check result normal?
Go to Step 26 .

    Check and repair harness between B-18 (terminal No. 11, terminal No. 12 and terminal No. 23) engine-ECU connector and body earth.

    • Check earthing line for open circuit or damage.

STEP 26. Check harness between battery and A-33X (terminal No. 3 and terminal No. 4) engine control relay 1 connector.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 27 .
Repair the damaged harness wire.

STEP 27. Check harness between A-33X (terminal No. 1) engine control relay 1 connector and B-18 (terminal No. 42) engine-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 28 .
Repair the damaged harness wire.

STEP 28. Check harness between A-33X (terminal No. 2) engine control relay 1 connector and A-21X (terminal No. 2 and terminal No. 4) engine control relay 2 connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 29 .
Repair the damaged harness wire.

STEP 29. Check harness between A-21X (terminal No. 3) engine control relay 2 connector and B-18 (terminal No. 24, terminal No. 36 and terminal No. 48) engine-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 30 .
Repair the damaged harness wire.

STEP 30. Check harness between A-33X (terminal No. 1) engine control relay 1 connector and B-18 (terminal No. 42) engine-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Replace the engine-ECU
Repair the damaged harness wire.