Inspection Procedure
2: The system is not turned on and off by operating the LDW switch.
caution
Before replacing
the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit
are normal.
COMMENTS ON TROUBLE SYMPTOM
If the system is not turned on and off by operating the LDW switch, the power supply circuit
to ETACS-ECU, the ETACS-ECU itself, the LDW switch, the power supply circuit to the LDW-ECU
or the LDW-ECU itself may be defective.
note
Prior to diagnosis, check the power supply circuit to the ETACS-ECU. If no faults are
detected, follow this troubleshooting procedure.
PROBABLE CAUSES
Defective power supply circuit to the ETACS-ECU
The ETACS-ECU may be defective
Malfunction of the LDW switch
Defective LDW-ECU circuit system
Malfunction of the LDW-ECU
Damaged harness wires and connectors
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III diagnosis code
Check if diagnosis code is set to the LDW.
Q.
Is the diagnosis code set?
Troubleshoot the LDW-ECU. Refer to .
Go to Step 2
STEP 2 M.U.T.-III other system service data
Using the ETACS-ECU service data, check the LDW switch signal.
When the LDW switch is pressed.
Item No.
Item name
Normal condition
Item 405
LDW switch
ON
When the LDW switch is not pressed.
Item No.
Item name
Normal condition
Item 405
LDW switch
OFF
OK: Normal condition is displayed.
Q.
Is the check result normal?
Go to Step 3
NO : Troubleshoot the ETACS-ECU. Refer to Inspection Procedure 16 "The LDW switch signal
is not received" .
STEP 3. Voltage measurement at LDW-ECU connector (IG terminal).
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Check the voltage between the LDW-ECU connector (IG terminal) and body earth. OK: System voltage
Q.
Is the check result normal?
Go to Step 5.
Go to Step 4.
STEP 4. Check of open circuit in IG line between LDW-ECU and ETACS-ECU
connector.
Q.
Is the check result normal?
Repair the power supply circuit (between battery and ETACS-ECU).
Repair the connector(s) or wiring harness.
STEP 5. Resistance measurement at LDW-ECU connector (GND terminal)
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Measure the resistance between the LDW-ECU connector (GND terminal) and body earth. OK: Continuity exists (2 Ω or less)
Q.
Is the check result normal?
Go to Step 7.
Go to Step 6.
STEP 6. Check of open circuit in GND line between LDW-ECU connector
and body earth.
Q.
Is the check result normal?
The trouble can be an 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. M.U.T.-III data list
Check the LDW-ECU service data.
When the LDW switch is pressed.
Item No.
Item name
Normal condition
Item 18
LDW switch
ON
When the LDW switch is not pressed.
Item No.
Item name
Normal condition
Item 18
LDW switch
OFF
OK: Normal condition is displayed.
Q.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How
to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Troubleshoot the LDW-ECU. Refer to 
Go to Step 2