Description and Operation

General Information

The Supplemental Restraint System (SRS) is designed to supplement the seat belts to reduce the risk or severity of injury to the driver and passenger by deploying the driver, passenger, side airbags and seat belt pretensioners in certain frontal or side collisions. The SRS (airbag) consists of: the driver airbag module, located in the center of the steering wheel, which contains a folded airbag and inflator; the passenger airbag module, located in the instrument panel on the passenger side, which contains a folded airbag assembly with inflator unit; the side airbag modules, located in the front seats, which contain a folded airbag and inflator; and the curtain airbag modules, located inside the headliner, which contain folded airbags and inflator units. The SRS airbag crash detection function is performed by an electronic accelerometer that constantly measures vehicle acceleration and outputs a corresponding signal through the amplification and filtering circuit of the microprocessor. The SRSCM (SRS Control Module) detects a frontal impact using the frontal impact sensors and the internal acceleration sensors inside the SRSCM. For a side impact, the SRSCM detects a side impact using 4 side impact sensors, 2 conventional acceleration sensors at the internal locations of the center pillars, and 2 pressure sensors in the side of the front door module, and an internal acceleration sensor inside the SRSCM. The SRSCM is designed to issue a deployment command to the corresponding airbag module(s) using the sensor inputs described above.

1. 1
   DC/DC Converter: The DC/DC converter in the power supply unit includes a step-up/step-down transformer converter and provides the ignition voltage for all squib circuits. It is implemented as an ASIC, and the internal operating voltage of the SRSCM itself. If the internal operating voltage is below the critical setting value, it will perform a reset.
2. 2
   Backup Power Supply: The SRSCM has a separate backup power supply that instantly supplies deployment energy in a low-voltage condition or in the event of a power failure resulting from a frontal collision.
3. 3
   Self-Diagnosis: The SRSCM constantly monitors the current SRS operating state and system malfunction detection. When the vehicle power is turned off, system malfunctions can be checked using the trouble codes via GDS.
4. 4
   Airbag Warning Lamp On: When a fault is detected, the module sends a signal to the SRSCM warning lamp located on the cluster. The MIL lamp indicates an SRS fault to the driver. When the ignition is turned on, the SRS lamp illuminates for approximately six seconds.
5. 5
   Diagnostic Trouble Code Recording: When a malfunction occurs in the system, the SRSCM will store the DTC corresponding to the malfunction. The DTC can only be erased using the GDS. However, if an internal malfunction code is active or a failure has been recorded, troubleshooting cannot be performed.
6. 6
   Self-Diagnosis Connector: Data stored in the SRSCM memory is output to the GDS or other external output devices through the connector located under the protective cover on the driver's side.
7. 7
   After the airbag has deployed, the SRSCM must not be reused and must be replaced.
8. 8
   The SRSCM determines whether the passenger has fastened the seat belt by the signal from the built-in switch in the seat belt buckle, and deploys the front passenger airbag at each set impact speed.
9. 9
   Side airbag deployment is determined by the SRSCM, which detects the satellite sensor impact signal in a side collision, regardless of the seat belt status.