Inspection Procedure C-4

INSPECTION PROCEDURE C-4: Central Door Locking System: All the doors do not lock or unlock with just the door lock key cylinder key Operation.

TECHNICAL DESCRIPTION (COMMENT)
The door lock key cylinder switch or the ETACS-ECU may be defective.

TROUBLESHOOTING HINTS
- The door lock key cylinder switch 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: Test Harness Set
- MB991502: Scan Tool (MUT-II)
- MB991529: Diagnostic Trouble Code Check Harness

STEP 1. Check method of the input signal

Q: Which is to be used, the scan tool or a voltmeter to check the input signal?
Scan tool MB991502 : Go to Step 2.
Voltmeter : Go to Step 3.

STEP 2. Check the input signal (by using scan tool MB991502).
Check the input signal from the defective door lock key cylinder switch.

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 scan tool MB991502 to the data link connector.
2. Check that the tone alarm of scan tool MB991502 sounds when the input signal enters.

Q: Does the tone alarm of scan tool MB991502 sound when the input signal enters?

YES : Replace the ETACS-ECU. All doors should be locked or unlocked by using the door lock key cylinder switch.

NO : Scan tool MB991502 does not sound when the driver's or passenger's door lock key cylinder is turned from the neutral (off) position to "LOCK" or "UNLOCK": Refer to Inspection Procedure O-9 "The driver's or passenger's door lock key cylinder switch signal is not sent to the ETACS-ECU.

STEP 3. Check the input signal (by using a voltmeter).
Check the input signal from the defective door lock key cylinder switch.




1. Use special tool MB991529 to connect a voltmeter between ground terminal 4 or 5 and ETACS-ECU terminal 9 of the data link connector.
2. Check that the voltmeter indicator deflects once when the input signal enters.

Q: Does the voltmeter indicator deflect?

YES : Replace the ETACS-ECU. All doors should be locked or unlocked by using the door lock key cylinder switch.

NO : The voltmeter needle does not fluctuate when the driver-s or passenger's door lock key cylinder is turned from the neutral (off) position to "LOCK" or "UNLOCK": Refer to Inspection Procedure O-11 "The door lock switch (incorporated in power window main switch and power sub-switch) signal is not sent to the ETACS-ECU.