Inspection Procedure 4

Inspection Procedure 4: Headlights do not illuminate when the passing switch is operated.

CAUTION:
Whenever the ECU is replaced, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.

TECHNICAL DESCRIPTION (COMMENT)

If both headlights (low-beam and high-beam) do not illuminate, the passing switch input circuit or ETACS-ECU may have a problem.

TROUBLESHOOTING HINTS

- Malfunction of column switch
- Malfunction of the ETACS-ECU
- Damaged harness wires and connectors

DIAGNOSIS

Required Special Tools:

- MB991223: Harness set
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)

STEP 1. Check that the headlights operate.

Check that the low-beam and high-beam headlights illuminate normally.

Q. Is the check result normal?

YES Go to Step 2.
NO Refer to Inspection Procedure 1 "None of headlights (low-beam) illuminates." Inspection Procedure 1 and Inspection Procedure 2 "None of headlights (high-beam) illuminates." Inspection Procedure 2.
STEP 2. Using scan tool MB991958, read the ETACS-ECU diagnostic trouble code.





(1)
CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

Connect scan tool MB991958. Refer to "How to connect scan tool (M.U.T.-III) Reading and Clearing Diagnostic Trouble Codes."
(2)Turn the ignition switch to the "ON" position.
(3)Check whether the ETACS-ECU related DTC is set.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC set?

YES Diagnose the ETACS-ECU. Refer to ETACS, Diagnosis Electronic Time and Alarm Control System (ETACS).

NO Go to Step 3.

STEP 3. Retest the system

Q. Do the headlights (low-beam and high-beam) illuminate normally when turning ON the passing switch?

YES The trouble can be an intermittent malfunction How to Cope With Intermittent Malfunctions).
NO Replace the ETACS-ECU.