Inspection Procedure I-3

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

Headlight Relay (High-beam) Circuit:

NOTE: This troubleshooting requires use of scan tool MB991502 and SWS monitor kit MB991862. For details of how to use the SWS monitor, refer to "How to use SWS monitor".

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: Test Harness Set
- MB991502: Scan Tool (MUT-II)
- MB991862: SWS monitor kit

STEP 1. Use scan tool to select "ECU CHECK" on the SWS monitor display.
Check the following ECUs:
- column-ECU
- front-ECU

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502. Also connect SWS monitor kit MB991862 after turning on scan tool MB991502.







1. Connect scan tool MB991502 to the data link connector.
2. Connect SWS monitor kit MB991862 to the column switch connector.
3. When the ignition switch is turned to the "LOCK" (OFF) position, scan tool MB991502 should show "OK" on the "ECU CHECK" menu.

Q: Are "OK" displayed on the "COLUMN ECU" and "FRONT ECU"?
"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 service data of the SWS monitor.
Check the input signals from the following switches:
- ignition switch: ON
- lighting switch: HEAD
- dimmer switch: ON










Select "LIGHTING - HEADLIGHT HI" (FUNCTION DIAG), and 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"?

YES: Replace the front-ECU. Check that the headlights (high beam) illuminate normally.

NO:
- Normal condition is not displayed on the "HEADLIGHT SW": Refer to Inspection Procedure L-5 "ETACS-ECU does not receive a signal from the headlight switch."
- Normal condition is not displayed on the "DIMMER SW": Refer to Inspection Procedure L-5 "ETACS-ECU does not receive a signal from the dimmer switch."
- Normal condition is not displayed on the "H/L AUTO-CUT": Refer to Inspection Procedure I-8 "Headlight automatic shutdown function does not work normally."
- Normal condition is not displayed on the "FRONT ECU ACK": Replace the front-ECU. Check that the headlights (high beam) illuminate normally.