Inspection Procedure 2

Inspection Procedure 2: The interior alarm does not work normally while the theft-alarm is triggered.

CAUTION:
Before replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.

TECHNICAL DESCRIPTION (COMMENT)

If the interior alarm does not work normally, ETACS-ECU, or combination meter built-in tone alarm may have a problem.

TROUBLESHOOTING HINTS

- The ETACS-ECU may be defective
- Combination meter 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:

- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.





(1)
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 scan tool MB991958. Refer to "How to connect the Scan Tool (M.U.T.-III) Scan Tool Testing and Procedures."
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the CAN bus line found to be normal?

YES Go to Step 2.

NO Repair the CAN bus line CAN Bus Diagnostics Chart).

STEP 2. Using scan tool MB991958, read the ETACS-ECU diagnostic trouble code.

Check if DTC is set to the ETACS-ECU.

(1)Turn the ignition switch to the "ON" position.

(2)Check whether the ETACS-ECU DTC is set.

(3)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC set?

YES Diagnose the ETACS-ECU (Refer to Electronic Time and Alarm Control System (ETACS)), and then go to Step 3.
NO Go to Step 3.
STEP 3. Using scan tool MB991958, check actuator test.

(1)Connect scan tool MB991958 to the data link connector.

(2)Turn the ignition switch to the "ON" position.

(3)Set scan tool MB991958 to the actuator test mode.

- Item 12: Tone alarm

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the check result normal?

YES Go to Step 4.
NO Replace the combination meter.
STEP 4. Retest the system.

Check that the theft-alarm works normally.

Q. Does the theft-alarm work normally?

YES The trouble can be an intermittent malfunction How to Cope With Intermittent Malfunctions).
NO Replace the ETACS-ECU.