Air Bag Systems: Description and Operation
GENERALThe supplemental restraint system (SRS) is designed to supplement the seat belt to help reduce the risk of severe injury to the driver and passenger by activating and deploying the driver, passenger, side airbag and belt pre-tensioner in certain frontal or side collisions.
The SRS (Airbag) consists of: a driver side airbag module located in the center of the steering wheel, which contains the folded cushion and an inflator unit; a passenger side airbag module located in the passenger side crash pad contains the folded cushion assembled with inflator unit side airbag modules located in the driver and passenger seat contains the folded cushion and an inflator unit; curtain airbag modules located inside the headliner which contains folded cushions and inflator units. The Passenger Occupant classification System (OCS) utilizes a sensor mat placed between the passenger seat cover and cushion pad to measure the occupant's loading force on the vehicle seat. Seat Track Position Sensor (STPS) is located in the driver and passenger seat it, interfaces with the SRS Control module (SRSCM) and will help determine whether to suppress either stage of the multi-stage airbag system. SRSCM is located under the center console. The impact sensing function of the SRSCM is carried out by electronic accelerometer that continuously measures the vehicle's acceleration and delivers a corresponding signal through amplifying and filtering circuitry to the microprocessor.
SRSCM (SRS CONTROL MODULE)
The SRS airbag system consists of electrical and electronic components. Be cautious of the airbag parts.
The SRSCM will detect front impact with an inside sensor, side impact with a side impact sensor, airbag deployment request signal, and determine airbag module deployment.
1. DC/DC converter: DC/DC converter in power supply unit includes up/down transformer converter, and provides ignition voltage for 2 front airbag ignition circuits and inside operation voltage. If inside operation voltage is below critical value setting, it will perform re-setting.
2. Safety sensor: The safety sensor is located in the airbag ignition circuit. The safety sensor will operate airbag circuit at any deployment condition and release airbag circuit safely at normal driving condition. The safety sensor is a double contact electro-mechanical switch that will close detecting deceleration above certain criteria.
3. Back up power supply: SRSCM has a separate back up power supply, it will supply deployment energy instantly in low voltage condition or upon power failure by front crash.
4. Self diagnosis: SRSCM will constantly monitor current SRS operation status and detect system failure when the vehicle power supply is on, system failure may be checked with trouble codes using the scan tool. (Hi-Scan)
5. Airbag warning lamp : Upon detecting error, the SRSCM will transmit a signal to the airbag warning lamp located in the duster. The lamp will indicate SRS error. When the ignition key is on, the SRS lamp will be turned on for about 6 seconds, then will be turned off for a self check. If it remains on, the error is indicated.
6. Trouble code registration: Upon error occurrence in the system, the SRSCM will store a DTC corresponding to the error. DTC can be cleared only by Hi-Scan.
7. Self diagnostic connector: Data stored in SRSCM memory will be output to the Hi-Scan or other external output devices through the data link connector located below the driver side crash pad.
8. Once the airbag is deployed, the SRSCM should not be used again and replaced.
9. SRSCM will determine whether a passenger has put on a seat belt using built-in switch signal in the seat belt buckle, and deploy the front passenger seat airbag accordingly.
10. Side airbag deployment will be determined by SRSCM that will detect satellite sensor impact signal upon side crash, irrespective to seat belt condition.