Inspection Procedure 22: Engine-A/T-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 4).
The engine-A/T-ECU (terminal No. 57) 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-A/T-ECU (terminal No. 34 and No. 43), sensor and actuator from the engine control relay (terminal No. 1).

FUNCTION

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

PROBABLE CAUSE

Failed engine control relay
Failed battery
Failed ignition switch
Open/short circuit in engine control relay circuit or loose connector contact
Open/short circuit in ignition switch-IG1 circuit or loose connector contact
Open circuit in engine-A/T-ECU circuit or loose connector contact
Failed engine-A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check battery voltage.

Measure battery voltage at 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: B-15X engine control relay connector

Q. Is the check result normal?

Go to Step 3 .

Repair or replace.

STEP 3. Check engine control relay itself.

Check engine control relay itself (Refer to ).

Q. Is the check result normal?

	Go to Step 4 .

	Replace engine control relay.

STEP 4. Perform voltage measurement at B-15X engine control relay connector.

Remove relay, and measure at 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 power supply line for open/short circuit.

STEP 5. Connector check: C-111 engine-A/T-ECU connector

Q. Is the check result normal?

Go to Step 6 .

Repair or replace.

STEP 6. Perform voltage measurement at C-111 engine-A/T-ECU connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 34 and earth, also between terminal No. 43 and earth.

OK: System voltage

Q. Is the check result normal?

Check earthing line for short circuit.

Go to Step 7 .

STEP 7. Check harness between B-15X (terminal No. 1) engine control relay connector and C-111 (terminal No. 34 and No. 43) engine-A/T-ECU connector.

note

Before checking harness, check intermediate connector C-116, and repair if necessary.

Check power supply line for open/short circuit and damage.

Q. Is the check result normal?

Go to Step 8 .

Repair.

STEP 8. Perform voltage measurement at C-111 engine-A/T-ECU connector.

Measure engine-A/T-ECU terminal voltage.
Ignition switch: ON
Voltage between terminal No. 50 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 11 .

Go to Step 9 .

STEP 9. Connector check: C-307 ignition switch connector

Q. Is the check result normal?

Go to Step 10 .

Repair or replace.

STEP 10. Check ignition switch itself.

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

Q. Is the check result normal?

	Check intermediate connector C-18, C-205 and C-202, and repair if necessary. If intermediate connector is normal, check and repair harness between C-307 (terminal No. 2) ignition switch connector and C-111 (terminal No. 50) engine-A/T-ECU connector. Check output line for open/short circuit.

	Replace ignition switch.

STEP 11. Check harness between B-15X (terminal No. 2) engine control relay connector and C-111 (terminal No. 57) engine-A/T-ECU connector.

Check earthing line for open circuit and damage.

Q. Is the check result normal?

Go to Step 12 .

STEP 12. Check harness between B-15X (terminal No. 3 and No. 4) engine control relay connector and battery.

note

Before checking harness, check intermediate connector A-16, and repair if necessary.

Check power supply line for damage.

Q. Is the check result normal?

Go to Step 13 .

Repair.

STEP 13. Check harness between C-307 (terminal No. 2) ignition switch connector and C-111 (terminal No. 50) engine-A/T-ECU connector.

note

Before checking harness, check intermediate connectors C-18, C-205 and C-202 and repair if necessary.

Check output line for damage.

Q. Is the check result normal?

Go to Step 14 .

Repair.

STEP 14. Check harness between C-111 (terminal No. 33 and No. 42) engine-A/T-ECU connector and body earth.

note

Before checking harness, check intermediate connector C-115 and repair if necessary.

Check earthing line for damage.

Q. Is the check result normal?

Replace engine-A/T-ECU.

Repair.