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DTC B1420: Side-airbag module (RH) (squib) system (short circuit between squib circuit terminals)
 
 
cautionIf DTC B1420 is stored in the SRS-ECU, always diagnose the CAN bus lines.
 
 
OPERATION
  • The SRS-ECU judges how severe a collision is by detecting signals from the side impact sensor installed on the lower side of the center pillar and the G-sensor in the SRS-ECU. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, the SRS air bag will inflate.
  • The ignition signal is input to the side-airbag module to inflate the side-airbag.
 
 
DTC SET CONDITIONS
This DTC is stored if there is abnormal resistance between the input terminals of the side-airbag module (RH) (squib).
 
 
TROUBLESHOOTING HINTS
  • Improper engaged connector or defective short spring*
  • Short between the side-airbag module (RH) (squib) circuit terminals
  • Damaged connector(s)
  • Malfunction of the SRS-ECU
note*: The squib circuit connectors integrate a "short" spring (which prevents the air bag from deploying unintentionally due to static electricity by shorting the positive wire to the ground wire in the squib circuit when the connectors are disconnected). Therefore, if connector is damaged or improperly engaged, the short spring may not be released when the connector is connected.
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-III), diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
Connect scan tool (M.U.T.-III). Refer to "How to connect the scan tool ."
(2) Turn the ignition switch to "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the check result satisfactory?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C, Diagnosis ).
 
STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is stored.
(1) Erase the DTC.
(2) Turn the ignition switch to "ON" position.
(3) Check if the DTC is stored.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the DTC stored?
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. Connector check: SRS-ECU, side-airbag module (RH).
(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. After disconnecting the SRS-ECU connector, connect it again.
(3) After disconnecting the side-airbag module (RH) connector, connect the connector again. For the side-airbag module (RH) connector disconnection, unlock the connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect the connector.
(4) Connect the negative battery terminal.
(5) After erasing the diagnostic trouble code memory, check the DTC again.
(6) Disconnect the negative battery terminal.
Is DTC B1420 stored?
Go to Step 4.
Replace the connector concerned.
 
STEP 4. 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 side-airbag module (RH) connector, unlock the connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect the connector.
(3) Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).
(4)
cautionDo not insert a probe directly into the terminal from the connector front side as the connector contact pressure may be weakened.
Insert the resistor harness probe from the back of side-airbag module (RH) harness side connector.
(5) Connect the negative battery terminal.
(6) After erasing the diagnosis trouble code memory, check the diagnostic trouble code again.
(7) Disconnect the negative battery terminal.
Is DTC B1420 stored?
Go to Step 5.
Replace the front seatback pad and frame assembly (Refer to ).
 
STEP 5. Resistance measurement at the 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 SRS-ECU connector.
(3)
dangerTo release the connector short spring in the following operations, disconnect this side-airbag module connector, and keep the squib circuit shorted.
Disconnect the side-airbag module (RH) connector, unlock the connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect the connector.
(4)
cautionThe short spring may not be released due to the insufficient insertion, thus insert for 4 mm (0.16 inch) or more.
Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between the SRS+, SRS- line and the short spring, and then release the short spring.
(5) Take the measurements below at the side-airbag module (RH) harness side connector.
  • Continuity between SRS+, SRS- line
OK: No continuity
Is the check result normal?
Go to Step 6.
Repair the wiring harness SRS+, SRS- line between the side-airbag module (RH) connector and the SRS-ECU connector.
 
STEP 6. Recheck for diagnostic trouble code.
Check again if the DTC is stored.
(1) Erase the DTC.
(2) Turn the ignition switch to the "ON" position.
(3) Check if the DTC is stored.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is DTC B1420 stored?
Replace SRS-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).