System Operation
SUPPLEMENTAL RESTRAINTS SYSTEM CONTROL MODULE(SRSCM)SRS CONTROL MODULE
SRS HARNESS
The SRS harness is wrapped in a yellow tube to be distinguished from other system harnesses. A shorting bar is included inside the wiring connectors of DAB, PAB, SAB and BPT inflator side. The shorting bar shorts the current flow the DAB, PAB, SAB and BPT module circuits 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 servicing the airbag module.
SRSCM INDEPENDENT LAMP ACTIVATION
The SRS malfunction indicator lamp (MIL) is located in the cluster giving information of SRS operating conditions by control signals from the SRSCM.
There are certain fault conditions in which the SRSCM (SRS Control Module) cannot function and thus cannot control the operation of the lamp. In these cases, the lamp is directly activated by appropriate circuitry that operates independently of the SRSCM, as follow:
1. Loss of ignition voltage supply to the SRSCM : lamp turned on continuously.
2. Loss of internal operating voltage lamp turned on continuously.
3. SRSCM not connected lamp turned on through shorting bar in wiring harness connector.
CLOCK SPRING
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.
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.
SIDE IMPACT SENSOR(SIS)
The release system for the side airbag consists of a SRSCM installed in the middle of the vehicle and two SIS one on the left-hand side and one on the right. Only the SRSCM is capable of deploying the airbags or the seat-belt pretensioners systems in the vehicle. In the dialog between the SRSCM and the SIS, it is the SRSCM that makes the deployment decision.
The SRSCM is supported with the side airbag function by two SIS, which act as intelligent acceleration sensors and as such back up the central airbag controller. Both the SIS continuously report the system status on the left and right-hand sides of the vehicle to the SRSCM.
It monitors the acceleration sensor continuously. The test results are reported to the SRSCM by means of periodic status signals.
WARNING: When the ignition is ON, never cause a sudden shock around the installation area of the satellite sensor by a hammer, etc. Otherwise it could cause the airbag system to unexpectedly deploy during servicing.
SRSCM
The 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)
The SRSCM will deploy the airbag modules by sensing the frontal impact sensed by the sensor built in to the SRSCM.
1. DC/DC convertor: The DC/DC converter in the power supply includes a step-up and a step-down converter, which provides the firing voltage for four 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 that closes if it experiences a deceleration exceeding a specified threshold.
3. Back-up power: The SRSCM reserves an energy reserve 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 SRS operating status while the ignition key is turned on and detects possible malfunctions in the system. The malfunction can be displayed in the form of a diagnostic trouble code using the Hi-Scan Pro.
5. MIL (Malfunction Indication Lamp) notification If any fault is detected, the SRSCM sends a signal to the indicator lamp on the instrument cluster to warn the vehicle driver.
The MIL indicator is the key item in notifying the driver of SRS faults. It verifies lamp and SRSCM operation by flashing 6 times when the ignition switch is first turned on.
6. Malfunction recording : Once a fault occurs in the system, the SRSCM records the fault in memory in the form of a DTC, which can only be erased by the Hi-Scan Pro.
7. Data link connector: SRSCM memory stored is linked through this connector located underneath the driver side crash pad to an external output device such as the Hi-Scan Pro.
8. What if only BPT's deploy.
9. Crash output
The crash output is used to unlock the doors in case of a crash. The crash output is : 0-200 A in OFF mode and 200mA in ON mode. During the unlock command, the switch is closed for 200 ms.