Inspection Procedure J-3

Headlight and Taillight: Headlights (high-beam) do not illuminate normally.

Headlight Relay (High-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
- The column switch (turn-signal light and lighting switch) may be defective
- The front-ECU may be defective
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- 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 CHK" 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 the DLC harness before connecting the column-ECU harness. Be sure to connect SWS monitor kit MB991862 after turning on scan tool MB991958.







1. Connect scan tool MB991958 to the data link connector.
2. Connect SWS monitor kit MB991862 to the column switch connector.
3. Turn the ignition switch to the "LOCK" (OFF) position.
4. Operate scan tool MB991958 according to the procedure below to display "ECU COMM CHK."
1. Select "SYSTEM SELECT."
2. Select "SWS."
3. Select "SWS MONITOR."
4. Select "ECU COMM CHK."

5. Scan tool MB991958 should show "OK" on the "ECU COMM CHK" menus for both the "COLUMN ECU" and the "FRONT ECU" menus.

Q: Is "OK" displayed on both the "COLUMN ECU" and "FRONT ECU" menus?

"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 not possible."

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

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







Operate scan tool MB991958 according to the procedure below to display "HEADLIGHT HI."
1. Select "SYSTEM SELECT."
2. Select "SWS."
3. Select "SWS MONITOR."
4. Select "FUNCTION DIAG."
5. Select "LIGHTING."
6. Select "HEADLIGHT HI."




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

Q: Are normal conditions displayed on the "HEADLIGHT SW", "DIMMER SW", "H/L AUTO-CUT" and "FRONT ECU ACK"?

Normal conditions are displayed for all the items : Replace the front-ECU. Verify 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 N-5 "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 N-5 "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. Verify that the headlights (high-beam) illuminate normally.