Inspection Procedure 18: Vehicle power cannot be turned "OFF".
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Before replacing the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit are normal.
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COMMENTS ON TROUBLE SYMPTOM
If the power supply cannot be shut down by pressing the engine switch, the system may not receive any correct vehicle speed information via CAN or the IG1 power supply system may be defective.
PROBABLE CAUSES
- Incorrect vehicle speed information (CAN signal)
- Damaged wiring harness or connector (short to earth or short to power supply in IG1 line)
- Malfunction of IG1 relay
- Malfunction of engine switch
- Malfunction of KOS&OSS-ECU
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-III to diagnose the CAN bus lines.
Q.
Is the check result normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting).
STEP 2. Check the M.U.T.-III Diagnosis code for other systems
Check that the engine-ECU set a diagnosis code.
Q.
Is the diagnosis code set?
Diagnose the engine-ECU (Refer to GROUP 13A, Troubleshooting 
).
Go to Step 3.
STEP 3. M.U.T.-III other system data list
Check the engine-ECU data list.
Item No.4: Vehicle speed signal (Refer to GROUP 13A - Data list reference table ).
Q.
Is the check result normal?
Go to Step 4.
Perform troubleshooting for engine-ECU (Refer to GROUP 13A, Troubleshooting ).
STEP 4. IG1 relay check
Check that the IG1 relay works normally (Refer to ).
Q.
Is the check result normal?
Go to Step 5.
Replace the IG1 relay.
STEP 5. Voltage measurement at IG1 relay connector (IG1 terminal)
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(1)Remove the IG1 relay , and measure at the wiring harness side.
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(2)Turn the engine switch from "LOCK" (OFF) position to "ON" position.
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(3)Measure the voltage between the IG1 relay connector (IG1 terminal) and body earth.
OK: System voltage
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(4)Turn the engine switch from "ON" position to "LOCK" (OFF) position.
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(5)Measure the voltage between the IG1 relay connector (IG1 terminal) and body earth.
OK: 1 V or less
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Q.
Is the check result normal?
Go to Step 7.
Go to Step 6.
STEP 6. Check of short to power supply, short to earth or open circuit in IG1 line between the KOS&OSS-ECU connector and the IG1 relay connector
Q.
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.
STEP 7. Check of open circuit in earth line between the IG1 relay connector and the body earth
Q.
Is the check result normal?
Go to Step 8.
Repair the wiring harness.
STEP 8. Voltage measurement at IG1 relay connector (IG1 line and power supply line)
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(1)Measure at the wiring harness side.
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(2)Measure the voltage between the IG1 relay connector (power supply line) and the body earth.
OK: System voltage
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Q.
Is the check result normal?
Go to Step 10.
Go to Step 9.
STEP 9. Check of short to power supply, short to earth or open circuit in power supply line between the fusible link connector and the IG1 relay connector
Q.
Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.
STEP 10. Voltage measurement at ETACS-ECU connector (IG1 line)
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Turn the engine switch from "LOCK" (OFF) position to "ON" position.
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(3)Measure the voltage between the ETACS-ECU connector (IG1 line) and the body earth.
OK: System voltage
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(4)Turn the engine switch from "ON" position to "LOCK" (OFF) position.
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(5)Measure the voltage between the ETACS-ECU connector (IG1 line) and the body earth.
OK: 1 V or less
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Q.
Is the check result normal?
Go to Step 11.
Repair the wiring harness, IG1 line between the ETACS-ECU connector and the fusible link.
STEP 11. Engine switch check
Continuity check of engine switch (Refer to ).
Q.
Is the check result normal?
Go to Step 12.
Replace the engine switch.
STEP 12. Check of the troubles
Check whether the engine is started (cranking is performed).
Q.
Is the check result normal?
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Replace the KOS&OSS-ECU and register the chassis number (Refer to ).