Electrical System Description

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)
SRSCM decides to deploy the airbag module by sensing the frontal impact sensed by the sensor built in to the SRSCM.

DC/DC Converter
The DC/DC converters of 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.

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.

Back-up Power
The SRSCM reserves an energy supply to provide deployment energy for a short second when the vehicle voltage is low or if lost in a vehicle frontal crash.

Malfunction Detection
The SRSCM continuously monitors the current SRS operation status while the ignition key is turned on and detects possible malfunction of the system. The malfunction can be displayed in the form of a diagnostic trouble code using Scan Tool.

MIL (Malfunction Indicator Lamp) Notification
If any fault is detected, the SRSCM sends a signal to the indicator lamp on the cluster to warn the vehicle driver.
The MIL indicator is the key item in notifying the driver of SRS faults. Verify lamp and SRSCM operation by flashing 6 times when the ignition switch is first turned on.

Malfunction Recording
Once a fault occurs in the system, the SRSCM records the fault in the memory in the form of DTC and the DTC can only be erased only by Scan Tool.

Data Link Connector
Data stored in he SRSCM memory is read by Scan Tool through the data link connector.

After firing the airbags once, the SRSCM cannot be used again and must be replaced.

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 mA in OFF mode and 200 mA in ON mode. In case of the unlock command, the switch is closed for 200 ms