Inspection Procedure M-3

Dome light: Dome Light Dimming Function does not Work 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

Interior Light Dimming Function:

CIRCUIT OPERATION
The ETACS-ECU operates the dome light dimming function according to the input signals from the following switches:
- Ignition switch (IG1): OFF
- Key reminder switch: ON
- Front door switches: OFF
- Driver's door lock actuator switch: LOCK or UNLOCK

TECHNICAL DESCRIPTION (COMMENT)
Is the dome lights do not dim normally, the input circuits from the switches described in "CIRCUIT OPERATION" or the ETACS-ECU may be defective.

TROUBLESHOOTING HINTS
- Malfunction of the key reminder switch
- Malfunction of the door switches
- Malfunction of the driver's door lock actuator switch
- Malfunction of the ETACS-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. Check the dome light.
If a door is opened while the dome light switch is at "door-linked" position, the dome light should illuminate.

Q: Does the dome light illuminate normally?

YES: Go to Step 2.

NO: Refer to Inspection Procedure M-1 "Dome light, luggage compartment light , trunk light and door-ajar indicator light does not illuminate or turn off normally does not illuminate or go out normally."

STEP 2. Use scan tool MB991958 to select "ECU COMM Check" on the SWS monitor display.
Check the ETACS-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" menus.

Q: Is "OK" displayed on the "ETACS ECU" menu?

YES: Go to Step 3.

NO: Refer to Inspection Procedure A-3 "Communication with ETACS-ECU is impossible."

STEP 3. Check the input signal by using "DATA LIST" of the SWS monitor.
Check the input signals from the following switches:
- Ignition switch: OFF
- Driver's or front passenger's door: open

1. Operate scan tool MB991958 according to the procedure below to display "ETACS ECU."
a. Select "Interactive Diagnosis."
b. Select "System select."
c. Select "SWS."
d. Select "SWS MONITOR."
e. Select "Data List."
f. Select "ETACS ECU."

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

Q: Does the scan tool display the items "IG SW (IG1)" and "FRONT DOOR SW" as normal condition?

Normal conditions are displayed for all the items: Go to Step 4.

Normal condition is not displayed for "IG SW (IG1)": Refer to Inspection Procedure O-2 "ETACS-ECU does not receive a signal from the ignition switch (IG1)."

Normal condition is not displayed for "FRONT DOOR SW": Refer to Inspection Procedure O-6 "ETACS-ECU does not receive a signal from the driver's or the front passenger's door switch."

STEP 4. Check the input signal (by using the Pulse Check)
Check the input signals from the following switches:
- key reminder switch

1. Operate scan tool MB991958 according to the procedure below to display "Pulse check."
a. Select "Interactive Diagnosis."
b. Select "System select."
c. Select "SWS."
d. Select "Pulse Checking."

2. Check if scan tool MB991958 sounds or not.

Q: Does scan tool MB991958 sound when the key reminder switch is operated?

YES: Replace the ETACS-ECU. Check that the dome light dimming function works normally.

NO: Refer to Inspection Procedure P-1 "ETACS-ECU does not receive a signal from the key reminder switch."