Inspection Procedure 19: Engine-ECU Power Supply, Engine Control Relay, Ignition Switch-IG1 System












OPERATION



  • Battery voltage is applied to the engine control relay (terminal No. 3 and No. 4).
  • Engine-ECU (terminal No. 73) applies current to the engine control relay coil by turning ON the power transistor in the unit in order to turn the relay ON.
  • When the engine control relay is turned ON, the battery power will be supplied from the engine control relay (terminal No. 2) to the engine-ECU, sensor and actuator.

FUNCTION



  • When the ignition switch ON signal is input into the engine-ECU via ETACS-ECU, the engine-ECU turns ON the engine control relay.This causes battery voltage to be supplied to the engine-ECU, sensor and actuator.

PROBABLE CAUSES



  • Failed battery
  • Failed engine control relay
  • Failed ignition switch
  • Open/short circuit or harness damage in the engine control relay circuit or loose connector contact.
  • Open/short circuit or harness damage in the ignition switch (IG) circuit or loose connector contact.
  • Open circuit or harness damage in the engine-ECU earth circuit or loose connector contact.
  • Failed ETACS-ECU
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check battery.

  • Battery check (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 itself.

  • Check engine control relay itself (Refer to Engine Control Relay Continuity Check ).

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 connector side.
  • Voltage between terminal No. 3, No. 4 and earth
OK: System voltage

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

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

    • Check power supply line for open/short circuit.

STEP 5. Connector check: B-30 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-30 engine-ECU connector.

  • Disconnect connector and measure at harness side.
  • Voltage between terminal No. 73 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-30 (terminal No. 73) engine-ECU connector.

    • Check signal line for open/short circuit.

STEP 7. Perform voltage measurement at B-30 engine-ECU connector.

  • Disconnect connector and measure at harness side.
  • Short-circuit B-30 engine-ECU connector terminal No. 73 to the earth.
  • Voltage between terminal No. 82 and earth.
OK: System voltage

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

    Check and repair harness between the B-30 (terminal No. 82) engine-ECU connector and A-33X (terminal No. 2) engine control relay connector.

    • Check output line for open/short circuit.

STEP 8. Check harness between B-30 (terminal No. 82) engine-ECU connector and A-33X (terminal No. 2) engine control relay connector.

  • Check output line for damage.

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

STEP 9. Check harness between B-30 (terminal No. 73) engine-ECU connector and A-33X (terminal No. 1) engine control relay connector.

  • Check signal line for damage.

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

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

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 11 .
Repair the damaged harness wire.

STEP 11. Perform voltage measurement at B-30 engine-ECU connector.

  • Disconnect connector and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 92 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 16 .
Go to Step 14 .

STEP 14. Connector check: C-210 ignition switch connector

Q. Is the check result normal?
Go to Step 15 .
Repair or replace the connector.

STEP 15. Check ignition switch itself.

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

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 signal line for open/short circuit.
Replace the ignition switch.

STEP 16. 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-30 (terminal No. 92) engine-ECU connector.

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

STEP 17. Check harness between C-304 (terminal No. 10) ETACS-ECU connector and B-30 (terminal No. 92) engine-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 18 .
Repair the damaged harness wire.

STEP 18. 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 19 .
Replace the ETACS-ECU.

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 the damaged harness wire.

STEP 20. Check harness between B-30 (terminal No. 81 and No. 93) engine-ECU connector and body earth.

  • Check earthing line for open circuit and damage.

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