Air Bag Control Module: Description and Operation

The air bag diagnostic unit receives its main power from the AIR BAG fuse and reserve power from the METER fuse. Two collision sensitive sensors in the air bag diagnostic unit are in series with each other and with the Battery and both air bags. When both sensors close simultaneously, squibs in both air bag modules will be initiated. The air bag diagnostic unit also contains a back-up power supply and a self-diagnostic function.

If any faulty condition occurs, air bag diagnostic unit detects it and records the fault code into internal memory, and lights air bag warning lamp to warn it to driver.


Two collision-sensitive sensors are located in Air bag Diagnostic Unit (ADU). These two sensors (Safing sensor and G-sensor) and are electrically connected in series with air bag and battery.

In case of the frontal crash, the G-sensor gets the collision deceleration The collision deceleration information is converted into digital data and transmitted to CPU(Central Processing Unit). The CPU calculates the digital data and compares them with designed data to decide whether it has to send a signal to deploy the air bag module or not. If the calculation result by the CPU is correspond to the designed data, it decides to send a deployment signal.

At the same moment, the safing sensor, which is linked linearly on deployment circuit, checks whether the deceleration is happened by actual physical collision, or by other electronic waves and mal effect. So, only when both the signal of deployment from the CPU and closing of safing sensor switch come together, the air bag can be deployed.

Air Bag Diagnostic Unit (ADU) contains CPU, memory, auxiliary power supply and G-sensor and safing sensor. Auxiliary power supply is installed to guarantee deployment of air bag even when battery voltage is cut off in a collision.

CPU not only triggers air bag deployment but also performs procedures. CPU initiates a test sequence every time ignition key is turned "ON" and meanwhile, Air Bag Indicator is illuminated for 4-6 seconds. When sequence is completed and no fault is found, lamp goes out. If any failure is discovered, warning lamp will stay "ON" or flicker to warn driver. Even while driving, CPU continually monitors circuits and components of air bag system. If a failure occurs within system while driving, warning lamp is immediately illuminated. Contents of those detected failures are stored in memory and can be read with Kia Data Pro-II Tool.