Inspection Procedure J-3

Headlight, Tail Light: Headlights (High-beam) do not Illuminate Normally.

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

Headlight Relay (Hi-beam) Circuit:

CIRCUIT OPERATION
When the dimmer switch is turned on, the column switch sends a signal to the front-ECU.Then the front-ECU switches the headlights from low-beam to high beam or vice versa.

TECHNICAL DESCRIPTION (COMMENT)
If the headlights (high beam) do not illuminate normally, the column switch or the front-ECU may be defective.

TROUBLESHOOTING HINTS
- Malfunction of column switch (turn-signal light and lighting switch)
- Malfunction of the front-ECU
- Damaged harness wires or 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

STEP 1. Use scan tool MB991958 to select "ECU COMM Check" on the SWS monitor display.
Check the following ECUs:
- 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 "COLUMN ECU" and "FRONT ECU" menus.

Q: Are "OK" displayed on the "COLUMN ECU" and "FRONT ECU" menu?

"OK" are displayed for all the items: Go to Step 2.

"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."







STEP 2. Check the input signal by using "FUNCTION DIAG." menu of the SWS monitor.
Check the input signals from the following switches:
- Ignition switch: ON
- Lighting switch: HEAD
- Dimmer switch: ON

1. Operate scan tool MB991958 according to the procedure below to display "HEADLIGHT HI."
a. Select "Interactive Diagnosis."
b. Select "System select."
c. Select "SWS."
d. Select "SWS MONITOR."
e. Select "Function Diag."
f. Select "LIGHTING."
g. Select "HEADLIGHT HI."




2. Check that normal conditions are displayed on the items described in the given table.

Q: Does the scan tool display the items "HEADLIGHT SW", "DIMMER SW", "H/L AUTO-CUT" and "FRONT ECU ACK" as normal condition?

Normal conditions are displayed for all the items: Replace the front-ECU. Check that the headlights (high beam) illuminate normally.

The scan tool does not show the respective normal condition for item "HEADLIGHT SW": Refer to Inspection Procedure O-7 "ETACS-ECU does not receive a signal from the headlight switch."

The scan tool does not show the respective normal condition for item "DIMMER SW": Refer to Inspection Procedure O-7 "ETACS-ECU does not receive a signal from the dimmer switch."

The scan tool does not show the respective normal condition for item "H/L AUTO-CUT": Refer to Inspection Procedure J-9 "Headlight automatic shutdown function does not work normally."

The scan tool does not show the respective normal condition for item "FRONT ECU ACK": Replace the front-ECU. Check that the headlights (high beam) illuminate normally.