Inspection Procedure 19: Engine-ECU Power Supply, Engine Control Relay, Ignition Switch-IG1 System
OPERATION
- Battery voltage is applied to the engine control relay power supply line.
- Engine-ECU connector terminal C/R 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 connector terminal 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 KOS&OSS-ECU
- Open/short circuit or damage in the engine control relay circuit or loose connector contact.
- Open/short circuit or damage in the engine control relay circuit or loose connector contact.
- Open circuit or damage in the engine-ECU earth circuit or loose connector contact.
- Failed engine-ECU
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- Battery check (Refer to GROUP 54A - Battery - On-vehicle Service - Battery Test
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Q.
Is the check result normal?
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 Go to Step 2.
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 Replace the battery.
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STEP 2. Check engine control relay itself.
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- Check engine control relay itself (Refer to ).
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Q.
Is the check result normal?
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Go to Step 3.
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Replace the engine control relay.
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STEP 3. Voltage measurement at engine control relay connector (power supply line).
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(1)Remove the relay, and measure at the relay box side.
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(2)Check the voltage between the engine control relay connector (power supply line) and body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 4.
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Repair or replace the connector(s), or check and repair the harness of short to earth, and open circuit in power supply line between battery and engine control relay connector.
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STEP 4. Voltage measurement at engine-ECU connector (C/R terminal).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Check the voltage between the engine-ECU connector (C/R terminal) and body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 5.
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Repair or replace the connector(s), or check and repair the harness of short to earth, and open circuit in C/R line between engine control relay connector and engine-ECU connector.
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STEP 5. Voltage measurement at engine-ECU connector (BAT1 terminal).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Short-circuit engine-ECU connector (C/R terminal) to the body earth.
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(3)Check the voltage between the engine-ECU connector (BAT1 terminal) and body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 8.
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Go to Step 6.
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STEP 6. Check of short to earth, and open circuit in BAT1 line between engine control relay connector and engine-ECU connector.
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Q.
Is the check result normal?
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Go to Step 7.
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Repair the connector(s) or wiring harness.
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STEP 7. Check of harness damage in power supply line between the battery and engine control relay connector.
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Q.
Is the check result normal?
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Repair or replace the connector(s), or check and repair the harness of damage in C/R line between engine control relay connector and engine-ECU connector.
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Repair the connector(s) or wiring harness.
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STEP 8. Check of damage in BAT1 line between engine-ECU connector and engine control relay connector.
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Q.
Is the check result normal?
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Go to Step 9.
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Repair the connector(s) or wiring harness.
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STEP 9. Check of harness damage in power supply line between battery and engine control relay connector.
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Q.
Is the check result normal?
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Go to Step 10.
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Repair the connector(s) or wiring.
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STEP 10. Voltage measurement at engine-ECU connector (IGN terminal).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(3)Check the voltage between the engine-ECU connector (IGN terminal) and body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 13.
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Go to Step 11.
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STEP 11. Check IG1 relay itself.
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- Check IG1 relay itself (Refer to GROUP 42B - On-vehicle Service - Relay Inspection ).
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Q.
Is the check result normal?
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Go to Step 12.
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Replace the IG1 relay.
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STEP 12. Check of short to earth, and open circuit in IG1 line between IG1 relay connector and engine-ECU connector.
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Q.
Is the check result normal?
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Perform troubleshooting of OSS System (Refer to GROUP 42B - Troubleshooting - Trouble Symptom Chart ).
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Repair the connector(s) or wiring harness.
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STEP 13. Check of harness damage in IGN line between IG1 relay connector and engine-ECU connector.
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Q.
Is the check result normal?
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Go to Step 14.
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Repair the connector(s) or wiring harness.
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STEP 14. Check of open circuit and damage in GNDB, GNDE line between engine-ECU connector and body earth.
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Q.
Is the check result normal?
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Replace the engine-ECU.
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Repair the connector(s) or wiring harness.
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