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 or shorted engine control relay circuit, harness damage, or connector damage
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check battery voltage.

Measure battery voltage during cranking.

OK: 8 V or more

Q. Is the check result normal?

	Go to Step 2 .

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

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 9 .

	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 and damage.

Q. Is the check result normal?

	Replace the engine-ECU.

	Repair the damaged harness wire.

STEP 9. 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 15 .

	Go to Step 10 .

STEP 10. Connector check: C-304 and C-317 ETACS-ECU connectors

Q. Are the check results normal?

	Go to Step 11 .

	Repair or replace the connector.

STEP 11. 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 12 .

	Go to Step 13 .

STEP 12. 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.

Q. Are the check results 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 13. Connector check: C-210 ignition switch connector

Q. Is the check result normal?

	Go to Step 14 .

	Repair or replace the connector.

STEP 14. 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 15. 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 16 .

	Repair the damaged harness wire.

STEP 16. 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?

	Go to Step 17 .

	Repair the damaged harness wire.

STEP 17. 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 18 .

	Repair or replace the connector.

STEP 18. 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 19 .

	Repair or replace the connector.

STEP 19. 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.