Inspection Procedure 3: The headlamps (low-beam) illuminate regardless of the lighting switch positions. (High-beam does not illuminate)


caution
  • Before replacing the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit are normal.
  • When the ETACS-ECU of vehicles without KOS is replaced, the encrypted code of the ignition key needs to be registered to the ETACS-ECU. (If the encrypted code is not registered, the engine cannot be started. Register the encrypted code as described in Immobilizer System - How to Register Key ID .)
  • When the LDW-ECU is replaced, always initialise the LDW camera (Refer to ) and adjust the LDW camera image (Refer to ).

COMMENTS ON TROUBLE SYMPTOM


If the headlamps illuminate only at low-beam regardless of the lighting switch position, the headlamp fail-safe function may be active.

PROBABLE CAUSES



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. M.U.T.-III diagnosis code


Check if diagnosis code is set to the ETACS-ECU.

Q. Is the diagnosis code set?

Troubleshoot the ETACS-ECU. Refer to .

Go to Step 3.

STEP 3. M.U.T.-III other system diagnosis code


Check if diagnosis code is set to the ASC.

Q. Is the diagnosis code set?

YES : Troubleshoot the ASC. Refer to .

NO <Vehicles without lighting control sensor or vehicles without LDW> : Go to Step 6.

NO <Vehicles with lighting control sensor> : Go to Step 4.

NO <Vehicles with LDW> : Go to Step 5.

STEP 4. M.U.T.-III other system diagnosis code


Check if diagnosis code is set to the LIN.

Q. Is the diagnosis code set?

Refer to diagnosis code chart .

Go to Step 6.

STEP 5. M.U.T.-III other system diagnosis code


Check if diagnosis code is set to the LDW.

Q. Is the diagnosis code set?

Refer to diagnosis code chart .

Go to Step 6.

STEP 6. M.U.T.-III data list


Use the ETACS-ECU service data to check the signals related to the operation of auto lamp function.

Item No.
 Item name
 Normal condition
Item 348
 Head lamp switch (auto)
 ON
OK: Normal condition is displayed.

Q. Is the check result normal?

YES <Vehicles without auto lamp function> : Go to Step 8.

YES <Vehicles with auto lamp function> : Go to Step 7.

NO : Troubleshoot the ETACS-ECU. Refer to Inspection Procedure 11 "The column switch signal is not received" .

STEP 7. Photo sensor <Vehicles without lighting control sensor or vehicles without LDW> or lighting control sensor <Vehicles with lighting control sensor> or LDW-ECU (light sensor) <Vehicles with LDW> check


Check the photo sensor <Vehicles without lighting control sensor or vehicles without LDW> (Refer to ) or lighting control sensor <Vehicles with lighting control sensor> (Refer to ) or LDW-ECU (light sensor) <Vehicles with LDW> (Refer to ).

Q. Is the check result normal?

Go to Step 8.

Replace the photo sensor <Vehicles without lighting control sensor or vehicles without LDW> or lighting control sensor <Vehicles with lighting control sensor> or LDW-ECU (light sensor) <Vehicles with LDW>.

STEP 8. Retest the system


Check that the headlamps illuminate normally.

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 ).

Replace the ETACS-ECU.