Inspection Procedure A-10: The auto lamp function does not work normally. <Vehicles with lighting control sensor>


caution Before replacing the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit are normal.

OPERATION


The ETACS-ECU operates this function in accordance with the input signals from driving distance, lighting control sensor, and column switch (auto lamp switch). Also, when the column switch (lighting switch) is in the "AUTO" position, and when an abnormality is present to the auto lamp circuit, the fail-safe function is activated and the low beam is turned ON at all times regardless of the brightness around the vehicle.

COMMENTS ON TROUBLE SYMPTOM


If the auto lamp function does not work normally, the above input signal circuit(s) or the ETACS-ECU may have a problem.

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 in the LIN.

Q. Is the diagnosis code set?

Refer to diagnosis code chart .

Go to Step 3.

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


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

Q. Is the diagnosis code set?

Troubleshoot the ETACS-ECU (Refer to ).

Go to Step 4.

STEP 4. Check that the headlamps operate.


Check that the headlamps (low-beam) illuminate normally.

Q. Is the check result normal?

Go to Step 5.

Refer to Inspection Procedure A-1 "None of the low-beam headlamps illuminate." .

STEP 5. Lighting control sensor check


Check the lighting control sensor (Refer to ).

Q. Is the check result normal?

Go to Step 6.

Replace the lighting control sensor (Refer to ).

STEP 6. Retest the system


Check that the auto lamp function works 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 (Refer to ).