[Previous][Next]
Inspection Procedure 17: Vehicle power cannot be turned OFF.
 
 
cautionBefore replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.
 
 
 
 
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 ground or short to power supply in IG1 line)
  • Malfunction of IG1 relay
  • Malfunction of engine switch
  • Malfunction of KOS&OSS-ECU
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-III), diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the power supply mode of the engine switch to the "OFF" position before connecting or disconnecting scan tool (M.U.T.-III).
Connect scan tool (M.U.T.-III) [Refer to "How to connect scan tool (M.U.T.-III) "].
(2) Turn the power supply mode of the engine switch to "ON".
(3) Diagnose the CAN bus line.
(4) Turn the power supply mode of the engine switch to "OFF".
Is the CAN bus line found to be normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C, Troubleshooting ).
 
STEP 2. Using scan tool (M.U.T.-III), read the other system diagnostic trouble code.
Check whether the engine control module sets a diagnostic trouble code.
(1)
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the power supply mode of the engine switch to the "OFF" position before connecting or disconnecting scan tool (M.U.T.-III).
Connect scan tool (M.U.T.-III) [Refer to "How to connect scan tool (M.U.T.-III) "].
(2) Turn the power supply mode of the engine switch to "ON".
(3) Check if DTC is set.
(4) Turn the power supply mode of the engine switch to "OFF".
Is the DTC set?
Diagnose the engine control module (Refer to GROUP 13A, Troubleshooting ).
Go to Step 3.
 
STEP 3. Using scan tool (M.U.T.-III), check data list.
(1)
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the power supply mode of the engine switch to the "OFF" position before connecting or disconnecting scan tool (M.U.T.-III).
Connect scan tool (M.U.T.-III) [Refer to "How to connect the Scan Tool (M.U.T.-III) "].
(2) Turn the power supply mode of the engine switch to "OFF".
(3) Check the engine control module data list.
(1)
 
Item No.Item nameNormal condition
4Vehicle speedApproximately 40 km/h (25 mph)
OK: Normal condition are displayed.
Is the check result normal?
Go to Step 4.
Perform troubleshooting for engine control module (Refer to GROUP 13A, Troubleshooting ).
 
STEP 4. IG1 relay check.
Check that the IG1 relay works normally (Refer to ).
Is the check result normal?
Go to Step 5.
Replace the IG1 relay.
 
STEP 5. Voltage measurement at IG1 relay connector (IG1 terminal)
(1) Remove the IG1 relay, and measure at the wiring harness side.
(2) Turn the power supply mode of the engine switch to "ON".
(3) Measure the voltage between the IG1 relay connector (IG1 terminal) and body ground.
OK: System voltage
(4) Turn the power supply mode of the engine switch to "OFF".
(5) Measure the voltage between the IG1 relay connector (IG1 terminal) and body ground.
OK: 1 V or less
Is the check result normal?
Go to Step 7.
Go to Step 6.
 
STEP 6. Check of short to power supply, short to ground or open circuit in IG1 line between the KOS&OSS-ECU connector and the IG1 relay connector
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 ground line between the IG1 relay connector and the body ground
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)
(1) Remove the IG1 relay, and measure at the wiring harness side.
(2) Measure the voltage between the IG1 relay connector (power supply line) and the body ground.
OK: System voltage
Is the check result normal?
Go to Step 10.
Go to Step 9.
 
STEP 9. Check of short to power supply, short to ground or open circuit in power supply line between the fusible link connector and the IG1 relay connector
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)
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Turn the power supply mode of the engine switch to "ON".
(3) Measure the voltage between the ETACS-ECU connector (IG1 line) and the body ground.
OK: System voltage
(4) Turn the power supply mode of the engine switch to "OFF".
(5) Measure the voltage between the ETACS-ECU connector (IG1 line) and the body ground.
OK: 1 V or less
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 ).
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).
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 ).