Inspection Procedure C-6

Central Door Locking System: Forgotten Key Prevention 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

Forgotten Key Prevention Function Circuit:

CIRCUIT OPERATION
The ETACS-ECU operates the forgotten key prevention function according to the following switches:
- Key reminder switch: OFF
- Driver's or front passenger's door switch: ON
- Driver's or front passenger's door lock actuator switch: being turned on

The ETACS-ECU operates the forgotten key prevention function under the following conditions:
- Ignition key: inserted into the ignition key cylinder
- Driver's or front passenger's door: open
- Driver's or front passenger's door lock: being locked

TECHNICAL DESCRIPTION (COMMENT)
If the function does not work normally, the input circuit system from the switches or the ETACS-ECU may be defective (refer to "CIRCUIT OPERATION").

TROUBLESHOOTING HINTS
- Malfunction of the key reminder switch
- Malfunction of the driver's or front passenger's door switch
- Malfunction of the driver's or front passenger'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. 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 2.

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







STEP 2. Check the input signal by using "DATA LIST" of the SWS monitor.
Check the input signals from the following switches:
- Driver's door: open
- Front passenger's door: closed

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: The scan tool show the respective normal condition for item "FRONT DOOR SW."

YES: Go to Step 3.

NO: 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 3. Check the input signal (by using the pulse check mode of the monitor).
Check the input signals from the following switches:
- Key reminder switch
- Driver's or front passenger's door lock actuator 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. If the switches (see the given table), which are applicable for the input signal check, are operated, check if scan tool MB991958 sounds or not.

Q: Does scan tool MB991958 sound whenever the key reminder switch, the driver's and front passenger's door lock actuator switches are operated?

Normal conditions are displayed for all the items: Replace the ETACS-ECU. The forgotten key prevention function should work normally.

Scan tool MB991958 does not sound when the key reminder switch is operated: Refer to Inspection Procedure P-1 "ETACS-ECU does not receive a signal from the key reminder switch."

Scan tool MB991958 does not sound when the driver's or the front passenger's door lock actuator switch is operated: Refer to Inspection Procedure P-5 "ETACS-ECU does not receive a signal from the driver's or front passenger's door lock actuator switch."