Inspection Procedure C-6

Central Door Locking System: Forgotten key prevention function does not work normally.

NOTE: This troubleshooting procedure requires the use of scan tool MB991502 and SWS monitor kit MB991862. For details on how to use the SWS monitor, refer to "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 door lock actuator switch: being turned ON

The ETACS-ECU activates 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 electrically
- Driver's door lock: being locked manually

TECHNICAL DESCRIPTION (COMMENT)
If the forgotten key prevention function does not work normally, the input circuit from the switches or the ETACS-ECU may be defective.

TROUBLESHOOTING HINTS
- The key reminder switch may be defective
- The driver's or front passenger's door switch may be defective
- The driver's door lock actuator switch may be defective
- The ETACS-ECU may be defective
- The wiring harness or connectors may have loose, corroded or damaged terminals, or terminals pushed back in the connector

Required Special Tools:
- MB991223: Harness Set
- MB991502: Scan Tool (MUT-II)
- MB991862: SWS Monitor Kit

STEP 1. Use scan tool MB991502 to select "ECU COMM CHK" on the SWS monitor display.
Check the ETACS-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.




1. Connect the scan tool MB991502 to the data link connector (16-pin).
2. Connect the SWS monitor kit MB991862 to the data link connector (13-pin).
3. Turn the ignition switch to the "LOCK" (OFF) position.
4. Operate the scan tool MB991502 as follows:
1. Select "SYSTEM SELECT."
2. Select "SWS."
3. Select "SWS MONITOR."
4. Select "ECU COMM CHK".
5. Check the scan tool MB991502 should show "OK" on the "ETACS ECU" menu.

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 not possible."

STEP 2. Check the input signal by using "DATA LIST" menu of the SWS monitor.




Check the input signals from the following switches:
- Driver's door: open
- Front passenger's door: close

1. Operate the scan tool MB991502 as follows:
1. Select "SYSTEM SELECT."
2. Select "SWS."
3. Select "SWS MONITOR."
4. Select "DATA LIST."
5. Select "ETACS ECU."




2. Check that normal conditions are displayed on the items described in the 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 N-5 "ETACS-ECU does not receive signals from the front door switches."

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 door lock actuator switch

1. Operate the scan tool MB991502 as follows:
1. Select "SYSTEM SELECT."
2. Select "SWS."
3. Select "PULSE CHECK."




2. If the switches (see table), which are applicable for the input signal check, are operated, verify if scan tool MB991502 sounds or not.

Q: Does scan tool MB991502 sound whenever the key reminder switch and the driver's door lock actuator switch are operated?

YES: Replace the ETACS-ECU. Verify that the forgotten key prevention function works normally.

NO:
- Scan tool MB991502 does not sound when the key reminder switch is operated: Refer to Inspection Procedure O-1 "ETACS-ECU does not receive a signal from the key reminder switch."
- Scan tool MB991502 does not sound when the driver's door lock actuator switch is operated Refer to Inspection Procedure O-6 "ETACS-ECU does not receive a signal from the driver's door lock actuator switch."