Inspection Procedure H-5

INSPECTION PROCEDURE H-5: Headlight and Taillight: The headlamps illuminate at low-beam (high-beam does not illuminate) regardless of the lighting switch positions.

NOTE: This troubleshooting procedure requires the use of scan tool MB991958 and SWS monitor kit MB991813. For details on 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
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
- The front-ECU may be defective

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

- MB991813: SWS Monitor Kit
- MB991806: SWS Monitor Cartridge
- MB991812: SWS Monitor Harness (For Column-ECU)
- MB991822: 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 MB991910 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 "System select."
b. Select "SWS."
c. Select "SWS MONITOR."
d. Select "ECU COMM Check."

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

Q: Is "OK" displayed for both the "ETACS ECU", "COLUMN ECU" and "FRONT ECU" menus?

"OK" is displayed for all the items : Replace the front-ECU. Verify that the headlights and the taillights illuminate normally.

"NG" is displayed for the "ETACS ECU" menu : Refer to Inspection Procedure A-3 "Communication with the ETACS-ECU is not possible." Inspection Procedure A-3

"NG" is displayed for the "COLUMN ECU" menu : Refer to Inspection Procedure A-2 "Communication with the column switch (column-ECU) is not possible." Inspection Procedure A-2

"NG" is displayed for the "FRONT ECU" menu : Refer to Inspection Procedure A-4 "Communication with the front-ECU is not possible." Inspection Procedure A-4