B120B

DTC B120B Theft-alarm sensor error

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

TROUBLE JUDGMENT

The theft-alarm sensor communicates with the ETACS-ECU via the LIN bus line. If the diagnostic trouble code No. B120B is set, the theft-alarm sensor itself may be defective.
NOTE:

- Diagnostic trouble code No.B120B may be set when the theft-alarm sensor cover is improperly installed or is removed. Check if the theft-alarm sensor cover is properly installed.
- Diagnostic trouble code No.B120B is set when the ultrasonic wave transmission/reception part of the theft-alarm sensor is covered. Check if the ultrasonic wave transmission/reception part of the theft-alarm sensor was covered.

TROUBLESHOOTING HINTS

Malfunction of the theft-alarm sensor

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, read the ETACS-ECU diagnostic trouble code.

Check if DTC is set to 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 scan tool MB991958. Refer to "How to connect scan tool (M.U.T.-III) Reading and Clearing Diagnostic Trouble Codes."
(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)).

NO Go to Step 2.

STEP 2. Theft-alarm sensor operation check

Ultrasonic wave sensor check

1. With the windows of the vehicle opened, set the theft-alarm to the "Ready to be triggered" condition.

2. Put the arm from the outside to the inside of the vehicle.

3. Check that the theft-alarm siren sounds.

Tilt angle sensor check

4. With the windows of the vehicle opened, set the theft-alarm to the "Ready to be triggered" condition.

5. Raise the front wheels or rear wheels.

6. Check that the theft-alarm siren sounds.

Q. Is the check result normal?

YES The trouble can be an intermittent malfunction How to Cope With Intermittent Malfunctions).
NO Go to Step 3.
STEP 3. Using scan tool MB991958, read the ETACS-ECU diagnostic trouble code.

Check if diagnostic trouble code No. B120A is set to the ETACS-ECU.

Q. Is diagnosis trouble code No.B120A set?

YES Perform the troubleshooting of diagnosis trouble code No.B120A. (Refer to B120A)
NO [The ultrasonic wave sensor is defective, or the ultrasonic wave sensor and the inclination sensor are defective] : Go to step 4.
NO [Only the inclination sensor is defective] : Go to step 5.
STEP 4. Check the customize function.

Check if the ultrasonic wave sensor of the theft-alarm senor operates when the sensitivity of the theft-alarm senor is set to "Level 1".

Q. Is the check result normal?

YES The trouble can be an intermittent malfunction How to Cope With Intermittent Malfunctions).
NO Go to step 5.
STEP 5. Replace the theft-alarm sensor temporarily, and check whether the diagnostic trouble code is set.

Check again if the diagnostic trouble code is set to the ETACS-ECU.

(1)Erase the DTC.

(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.

(3)Check if DTC is set.

Q. Is the DTC set?

YES Replace the ETACS-ECU.
NO Replace the theft-alarm sensor.