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 (terminal No. 3 and No. 4).
  • The engine-ECU (terminal No. 131) makes the power transistor in the unit be in "ON" position and makes currents go on the engine control relay coil, and that makes the relay be in "ON" position.
  • When the engine control relay is in "ON" position, the battery voltage is supplied to the engine-ECU (terminal No. 61, terminal No. 62 and terminal No. 63), the sensor and the actuator from the engine control relay (terminal No. 2).
  • The engine-ECU (terminal No. 64, terminal No. 65 and terminal No. 66) 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: A-33X engine control relay connector

Q. Is the check result normal?
Go to Step 3 .
Repair or replace the connector.

STEP 3. Check engine control relay.

  • Check engine control relay (Refer to ).

Q. Is the check result normal?
Go to Step 4 .
Replace the engine control relay.

STEP 4. Perform voltage measurement at A-33X engine control relay 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 5 .

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

    • Check power supply line for open/short circuit.

STEP 5. Connector check: B-06 engine-ECU connector

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

STEP 6. Perform voltage measurement at B-06 engine-ECU connector.

  • Disconnect connector, and measure at the harness side.
  • Voltage between terminal No. 131 and earth.
OK: System voltage

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

    Check and repair harness between A-33X (terminal No. 1) engine control relay connector and B-06 (terminal No. 131) engine-ECU connector.

    • Check signal line for open/short circuit.

STEP 7. Perform voltage measurement at B-06 engine-ECU connector.

  • Disconnect connector, and measure at the harness side.
  • Using a jumper wire, connect terminal No. 131 to earth.
  • Ignition switch: ON
  • Voltage between terminal No. 61 and earth, between terminal No. 62 and earth also between terminal No. 63 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 11 .
Go to Step 8 .

STEP 8. Check harness between A-33X (terminal No. 2) engine control relay connector and B-06 (terminal No. 61, terminal No. 62 and terminal No. 63) engine-ECU connector.

  • Check output line for open/short circuit.

Q. Is the check result normal?
Go to Step 9 .
Repair the damaged harness wire.

STEP 9. Check harness between A-33X (terminal No. 1) engine control relay connector and B-06 (terminal No. 131) engine-ECU.

  • Check power supply line for damage.

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

STEP 10. Check harness between A-33X (terminal No. 3 and terminal No. 4) engine control relay connector and battery.

  • Check power supply line for damage.

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

STEP 11. Perform voltage measurement at B-06 engine-ECU connector.

  • Disconnect connector, and measure at the harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 144 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 17 .
Go to Step 12 .

STEP 12. Connector check: C-304 and C-317 ETACS-ECU connectors

Q. Are the check results normal?
Go to Step 13 .
Repair or replace the connector.

STEP 13. Perform voltage measurement at C-317 ETACS-ECU connector.

  • Disconnect connector and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 6 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 14 .
Go to Step 15 .

STEP 14. 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 the C-304 (terminal No. 10) ETACS-ECU connector and B-06 (terminal No. 144) engine-ECU connector.

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

STEP 15. Connector check: C-210 ignition switch connector

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

STEP 16. 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 17. 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?
Go to Step 18 .
Replace the ETACS-ECU.

STEP 18. Check harness between C-304 (terminal No. 10) ETACS-ECU connector and B-06 (terminal No. 144) engine-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 19 .
Repair or replace the connector.

STEP 19. 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 20 .
Repair or replace the connector.

STEP 20. Check harness between B-06 (terminal No. 64, terminal No. 65 and terminal No. 66) engine-ECU connector and body earth.

  • Check earthing line for open circuit damage.

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