Inspection Procedure J-5

Headlight, Tail Light: Headlights do not Illuminate When the Lighting Switch is at "AUTO," "TAIL," and "PASSING" Position, but Illuminate at Low-beam when the Switch is at "HEAD" Position. At this Position, the Headlights cannot be Changed into High Beam by Operating the Dimmer Switch.

NOTE: This troubleshooting requires use of scan tool MB991958 and SWS monitor kit MB991862. For details of how to use the SWS monitor, refer to "How to use SWS monitor." How To Use SWS Monitor

TECHNICAL DESCRIPTION (COMMENT)
If the headlights illuminate at low-beam regardless of the lighting switch positions, the headlight operation is in fail-safe mode.

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

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicles communication interface
- MB991827: MUT-III USB cable
- MB991911: MUT-III Main harness B
- MB991813: SWS monitor kit
- MB991806: SWS monitor cartridge
- MB991812: SWS monitor harness (for column-ECU)
- MB991922: Probe harness

Use scan tool MB991958 to select "ECU COMM Check" on the SWS monitor display.
Check the following ECUs:
- ETACS-ECU
- Column-ECU
- Front-ECU

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 special tool MB991911 before connecting special tool MB991812. Be sure to connect special tool MB991806 after turning on special tool MB991824.







1. Connect the special tool. Refer to "How to connect SWS monitor." How to Connect SWS Monitor
2. Turn the ignition switch to the "LOCK" (OFF) position.
3. Operate scan tool MB991958 according to the procedure below to display "ECU COMM Check."
a. Select "Interactive Diagnosis."
b. Select "System Select."
c. Select "SWS."
d. Select "SWS MONITOR."
e. Select "ECU COMM Check."

4. Scan tool MB991958 should show "OK" on the "ECU COMM Check" menus for both the "ETACS ECU," the "COLUMN ECU" and the "FRONT ECU" menus.

Q: Are "OK" displayed on the "ETACS ECU", "COLUMN ECU" and "FRONT ECU" menus?

"OK" are displayed for all the items: Replace the front-ECU. Check that the headlights and the tail lights illuminate normally.

"NG" is displayed on the "ETACS ECU" menu: Refer to Inspection Procedure A-3 "Communication with ETACS-ECU is impossible."

"NG" is displayed on the "COLUMN ECU" menu: Refer to Inspection Procedure A-2 "Communication with column switch (column-ECU) is impossible."

"NG" is displayed on the "FRONT ECU" menu: Refer to Inspection procedure A-4 "Communication with front-ECU is impossible."