CODE NO. B1B20 Right curtain air bag module (squib) system (shorted to squib circuit earth)











caution If the diagnosis code B1B20 is set to SRS-ECU, be sure to diagnose the CAN bus line.

OPERATION


In case of side collision, when the impact exceeding the threshold is applied to the vehicle, and when the impact is simultaneously detected (turned ON) by the side impact sensor installed to the lower part of centre pillar and to quarter panel inner as well as by the side-airbag safing G-sensor in SRS-ECU, the electric current is supplied from SRS-ECU to the curtain air bag module (squib) of impacted side.

TROUBLE JUDGMENT


The code is set when the SRS-ECU curtain air bag module (squib) circuit is shorted to earth.

PROBABLE CAUSES



  • Poor contact of connector
  • Curtain air bag module (squib) harness shorted to earth
  • Malfunction of SRS-ECU

DIAGNOSIS PROCEDURE


STEP 1. M.U.T.-III CAN bus diagnostics.


Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?

Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ).

STEP 2. Check whether the diagnosis code is reset.


(1)Connect the negative battery terminal.
(2)After erasing the diagnosis code memory, check the diagnosis code again.
(3)Disconnect the negative battery terminal.

Q. Is the diagnosis code No. B1B20 set?

Go to Step 3.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).

STEP 3. Diagnosis check by dummy resistor connection.


(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2)Disconnect the D-08 intermediate connector (connection between curtain air bag harness and floor harness).

(3)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).
(4)
caution Do not insert a probe directly into the terminal from the connector front side as the connector contact pressure may be weakened.
Insert the probe of resistor harness, to which the dummy resistor is installed, from the back of D-08 intermediate connector (floor harness side).
(5)Connect the negative battery terminal.
(6)After erasing the diagnosis code memory, check the diagnosis code again.
(7)Disconnect the negative battery terminal.

Q. Is the diagnosis code No. B1B20 set?

Go to Step 4.

Go to Step 5.

STEP 4. Resistance measurement at the C-31 SRS-ECU connector.


(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.

(2)While pushing the part "A" indicated in the figure of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever, and disconnect the C-31 SRS-ECU connector.
(3)Disconnect the D-08 intermediate connector (connection between curtain air bag harness and floor harness).

(4)
caution The short spring may not be released due to the insufficient insertion. Therefore, insert the insulator for 4 mm or more.
Insert an insulator (width: 3 mm, thickness: 0.5 mm) such as cable tie between the terminal No. 39 and 40, and then release the short spring.
(5)Check the continuity between C-31 wiring harness side connector terminal No. 39/40 and body earth.
OK: No continuity

Q. Is the check result normal?

Go to Step 6.

Repair the wiring harness.

STEP 5. Resistance measurement at the D-08 intermediate connector.


(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.

(2)
danger To release the D-08 intermediate connector short spring in the following operations, disconnect the D-103 air bag module harness side connector beforehand, and keep the squib circuit shorted.
Use the flat-tipped screwdriver to pull out the locking button of harness side connector. After releasing the lock, disconnect the D-103 harness side connector.
(3)Disconnect the D-08 intermediate connector (connection between curtain air bag harness and floor harness).

(4)Because the short spring is installed to the D-08 intermediate connector (curtain air bag harness side), insert an insulator (width: 3 mm, thickness: 0.5 mm) such as cable tie to the location shown in the figure, and release the short spring.
(5)
caution Do not insert a probe directly into the terminal from the connector front side as the connector contact pressure may be weakened.
Check the continuity between the D-08 intermediate connector (module side) terminal No. 1/2 and the body earth.
OK: No continuity

Q. Is the check result normal?

Replace the curtain air bag module (squib) (Refer to ).

Repair the wiring harness.

STEP 6. M.U.T.-III diagnosis code.


Q. Is the diagnosis code No. B1B20 set?

Replace SRS-ECU (Refer to ).
Intermittent Malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).