Air Bag Control Module: Description and Operation
SRSCMThe SRS airbag system has sophisticated electrical and electronic components. Therefore the airbag operating components should be handled very carefully.
SRSCM (Supplement Restraint System Control Module)
SRSCM determines when to deploy the airbag module by sensing the frontal and side impact force through the built in sensor SRSCM.
1. DC/DC convertor : The DC/DC convertors of the power supply includes a step up and a step down converter; which provide the firing voltage for six firing circuits and the internal operating voltage. If the internal operating voltage falls below a defined threshold a reset is executed.
2. Arming sensor/safing sensor : The arming/safing sensor built in to the airbag firing circuit has the function of arming the airbag circuit under all required deployment conditions and maintaining the airbag firing circuits unarmed under normal driving conditions. The safing sensor is a dual-contact electromechanical switch which closes if it experiences a deceleration exceeding a specified threshold.
3. Back-up power: The SRSCM has emergency energy reserves to provide deployment energy for a short period when the vehicle voltage is low or if lost in a vehicle frontal crash.
4. Malfunction detection : The SRSCM continuously monitors the current 8RS operation status while the ignition key is turned on and detects a malfunction of the system. The malfunction can be displayed in the form of diagnostic trouble code using Hi-scan.
5. MIL (Malfunction Indication Lamp) notification: If any fault is detected, the SRSCM sends a signal to the indicator lamp on the cluster to warn the vehicle's driver. The MIL indicator is the key to driver notification of SRS faults. Verify lamp and SRSCM operation by observing the flashinging 6 times when the ignition switch is first turned on.
6. Malfunction recording : Once a fault occurs in the system SRSCM records the fault in the memory in the form of DTC and the DTC is erased by Hi-scan.
7. Data link connector: The SRSCM memory stored data are linked through this connector located at the underneath of driver side crash pad to an external output device such as Hi-scan.
8. After firing the airbags once, the SRSCM cannot be used again and must be replaced.
9. Crash output
The crash output is used to control an external device which will unlock the doors in case of a crash event. The crash output is specified as follows:0-200 micro A in OFF mode and 200 mA in ON mode. In case of an unlock command the switch is closed for 200 mS.
SRS HARNESS
The SRS harness is wrapped in yellow tube to identify it from other system harnesses. A shorting bar is included inside the wiring connectors of DAB, PAB, DSAB, PSAB and BPT inflator side. The shorting bar shorts the current flow when the connectors are disconnected. The circuits to the inflator module are shorted in this way to help prevent unwanted deployment of the airbag when serving the airbag module.
CLOCK SPRING
The clock spring (coil spring) consists of two current carrying coils. It is attached between the steering column and the steering wheel. It allows rotation of the steering wheel while maintaining continuous contact of the deployment loop through the inflator module.
Clock Spring:
The steering wheel must be fitted correctly to the steering column with the clock spring at the neutral position, otherwise cable disconnection and other troubles may result.
OC (OCCUPANT CLASSIFICATION) SYSTEM (ONLY USA)
In contrast to the initial one-stage airbag Systems, newer restraint systems involve complex logic to select, or alternatively suppress, various levels of safety system deployment.
Inherent to an Advanced Restraint System is the ability to discern information regarding passenger occupancy. It is intended that these inputs be provided through the OCS. The objective of such safety system is to reduce the risk and level of injuries by automatically adapting the airbag(s) and seat belt pretensioner to the driving status of the vehicle, its occupants, and the crash severity.
The current OCS covered in this specification continually senses and classifies the front passenger side seat.
SIDE IMPACT SENSOR(ONLY USA)
The Side Impact Sensors are remote sensor that detect acceleration due to collision at their mounting locations. The primary purpose of the Side Impact Sensors is to provide an indication of a collision earlier than is possible from a central mounting location. The Side Impact Sensors send acceleration data to the central control module.
FRONT IMPACT SENSOR (ONLY USA)
The Front Impact Sensor is a remote sensor that provides accelerometer data to the advanced restraint control module to determine if the severity of a frontal impact event warrants a single-stage or dual-stage frontal airbag deployment.
STPS (SEAT TRACK POSITION SENSOR) (ONLY USA)
The STPS operated via a non-contacting magnetic proximity sensing device combined with a simple electronic circuit resulting in the ability of producing two separate & distinct logic level signals.
The STPS output signal is altered by the proximity of a separate ferro-magnetic shunt, which is linked via the seat track. The logic signal produced is the result of the proximity device being activated (no shunt present) or deactivated (shunt present).