B1421

DTC B1421: Side-Airbag Module (RH) (Squib) System Fault 2 (Open in the Squib Circuit)

Side-Airbag Module (RH) (Squib) Circuit (Part 1):

CAUTION: If DTC B1421 is set in the combination meter, always diagnose the CAN bus lines.

CIRCUIT OPERATION
- The SRS-ECU judges how severe a collision is by detecting signals from the left and right side impact sensors. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, if the side-airbag safing G-sensor is on, the SRS side-airbag will inflate.
- The ignition signal is input to the side-airbag module to inflate the side-airbag.

DTC SET CONDITIONS
This DTC is set if there is abnormal resistance between the input terminals of the side-airbag module (RH) (squib).

TROUBLESHOOTING HINTS
- Open circuit in the side-airbag module (RH) (squib) circuit
- Improper connector contact
- Malfunction of the SRS-ECU

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

- MB991865: Dummy resistor
- MB991866: Resister harness

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







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.

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

Q: Is the check result satisfactory?

YES : Go to Step 2

NO : Repair the CAN bus lines.

STEP 2. Recheck for diagnostic trouble code.







Check again if the DTC is set.

1. Erase the DTC.
2. Turn the ignition switch to "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES : Go to Step 3.

NO : There is an intermittent malfunction such as poor engaged connector(s) or open circuit.

STEP 3. Check the side-airbag module (RH). (Using scan tool MB991958, read the diagnostic trouble code.)

1. Disconnect the negative battery terminal.







2. Disconnect the side-airbag module (RH) connector D-28.







3. Connect special tool MB991865 to special tool MB991866.

CAUTION: Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

4. Insert special tool MB991866 into the D-28 harness side connector by backprobing.
5. Connect the negative battery terminal.
6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

Q: Is DTC B1421 set?

YES : Go to Step 4.

NO : Replace the seatback frame of the front seat (RH). Then go to Step 5.

STEP 4. Check the harness for open circuit between SRS-ECU connector C-124 (terminal No.57 and 58) and the side-airbag module (RH) connector D-28 (terminal No.2 and 1).

1. Disconnect the negative battery terminal.







2. Disconnect SRS-ECU connector C-124.







DANGER: To prevent the air bag from deploying unintentionally, disconnect the side-airbag module (RH) connector D-28 to short the squib circuit.

3. Disconnect side-airbag module connector D-28.







CAUTION: Insert an insulator such as a cable tie to a depth of 4mm (0.16 inch) or more, otherwise the short spring will not be released.

4. Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 57, 58 and the short spring to release the short spring.







CAUTION: Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

5. Check for continuity between the following terminals. It should be less than 2 ohms.
- SRS-ECU connector C-124 (terminal No.57) and the side-airbag module (RH) connector D-28 (terminal No.2)
- SRS-ECU connector C-124 (terminal No.58) and the side-airbag module (RH) connector D-28 (terminal No.1)

Q: Does continuity exist?

YES : Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1421 sets, replace the SRS-ECU. Then go to Step 5.

NO : Repair the harness wires between SRS-ECU connector C-124 and side-airbag module (RH) connector D-28 Then go to Step 5.

STEP 5. Recheck for diagnostic trouble code.







Check again if the DTC is set.

1. Erase the DTC.
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is DTC B1421 set?

YES : Return to Step 1.

NO : The procedure is complete.