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 <Vehicles without KOS>
Failed OSS-ECU <Vehicles with KOS>
Open/short circuit or harness damage in engine control relay circuit, or loose connector contact.
Open/short circuit or harness damage in ignition switch (IG1) circuit, or loose connector contact.
Open circuit or harness damage in 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-37X 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.

Engine control relay continuity check (Refer to ).

Q. Is the check result normal?

	Go to Step 4 .

	Replace the engine control relay.

STEP 4. Perform voltage measurement at A-37X engine control relay connector

Remove relay, and measure at relay box 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-37X (terminal No. 3 and No. 4) engine control relay connector. Check power supply line for open/short circuit.

STEP 5. Connector check: B-27 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-27 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-37X (terminal No. 1) engine control relay connector and B-27 (terminal No. 73) engine-ECU connector. Check signal line for open/short circuit.

STEP 7. Perform voltage measurement at B-27 engine-ECU connector.

Disconnect connector, and measure at harness side.
Short-circuit B-27 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 10 .

	Go to Step 8 .

STEP 8. Check harness between A-37X (terminal No. 2) engine control relay connector and B-27 (terminal No. 82) 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 the battery and A-37X (terminal No. 3) engine control relay connector.

Check power supply line for damage.

Q. Is the check result normal?

	Check and repair harness between A-37X (terminal No. 1) engine control relay connector and B-27 (terminal No. 73) engine-ECU connector. Check signal line for damage.

	Repair the damaged harness wire.

STEP 10. Check harness between B-27 (terminal No. 82) engine-ECU connector and A-37X (terminal No. 2) engine control relay connector.

Check output line for damage.

Q. Is the check result normal?

	Go to Step 11 .

	Repair the damaged harness wire.

STEP 11. Check harness between battery and A-37X (terminal No. 4) engine control relay connector.

Check power supply line for damage.

Q. Is the check result normal?

	Go to Step 12 .

	Repair the damaged harness wire.

STEP 12. Perform voltage measurement at B-27 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?

	YES : Go to Step 20 <Vehicles without KOS> .

	YES : Go to Step 22 <Vehicles with KOS> .

	Go to Step 13 .

STEP 13. Connector check: C-403 and C-417 ETACS-ECU connectors

Q. Are the check results normal?

	Go to Step 14 .

	Repair or replace the connector.

STEP 14. Perform voltage measurement at C-417 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 19 .

	NO : Go to Step 15 <Vehicles without KOS> .

	NO : Go to Step 17 <Vehicles with KOS> .

STEP 15. Connector check: C-309 ignition switch connector

Q. Is the check result normal?

	Go to Step 16 .

	Repair or replace the connector.

STEP 16. Check ignition switch itself.

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

Q. Is the check result normal?

	Check and repair harness between C-309 (terminal No. 2) ignition switch connector and C-417 (terminal No. 6) ETACS-ECU connector. Check signal line for open/short circuit.

	Replace the ignition switch.

STEP 17. Connector check: C-14 OSS-ECU connector

Q. Is the check result normal?

	Go to Step 18 .

	Repair or replace the connector.

STEP 18. Check harness between C-14 (terminal No. 7) OSS-ECU connector and C-417 (terminal No. 6) ETACS-ECU connector.

Check power supply line for open/short circuit.

Q. Is the check result normal?

	Perform troubleshooting of OSS System (Refer to GROUP 42B - Troubleshooting - Trouble Symptom Chart ).

	Repair the damaged harness wire.

STEP 19. Continuity check on C-417 and C-403 ETACS-ECU connectors

Disconnect connectors, and measure at the ETACS-ECU side.
Continuity test between terminal No. 6 (C-417) and No. 10 (C-403).

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-403 (terminal No. 10) ETACS-ECU connector and B-27 (terminal No. 92) engine-ECU connector. Check signal line for open/short circuit.

	Replace the ETACS-ECU.

STEP 20. Connector check: C-309 ignition switch connector and C-403 and C-417 ETACS-ECU connectors

Q. Are the check results normal?

	Go to Step 21 .

	Repair or replace the connector.

STEP 21. Check harness between C-309 (terminal No. 2) ignition switch connector and C-417 (terminal No. 6) ETACS-ECU connector.

Check signal line for damage.

Q. Is the check result normal?

	Go to Step 24 .

	Repair the damaged harness wire.

STEP 22. Connector check: C-14 OSS-ECU connector and C-403 and C-417 ETACS-ECU connectors

Q. Are the check results normal?

	Go to Step 23 .

	Repair or replace the connector.

STEP 23. Check harness between C-14 (terminal No. 7) OSS-ECU connector and C-417 (terminal No. 6) ETACS-ECU connector.

Check signal line for damage.

Q. Is the check result normal?

	Go to Step 24 .

	Repair the damaged harness wire.

STEP 24. Continuity check on C-417 and C-403 ETACS-ECU connectors

Disconnect connectors, and measure at the ETACS-ECU side.
Continuity test between terminal No. 6 (C-417) and No. 10 (C-403).

note

Connect the (+) side of circuit tester to terminal No. 10.

OK: Continuity

Q. Is the check result normal?

	Go to Step 25 .

	Replace the ETACS-ECU.

STEP 25. Check harness between C-403 (terminal No. 10) ETACS-ECU connector and B-27 (terminal No. 92) engine-ECU connector.

Check signal line for damage.

Q. Is the check result normal?

	Go to Step 26 .

	Repair the damaged harness wire.

STEP 26. Check harness between B-27 (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.