ETR Control Module with Airbag, Function

The airbag control module (N2/7) receives the following data from the 2 integrated redundant acceleration sensors
- Deceleration acting on the longitudinal axis of the vehicle during a head-on collision
- Acceleration acting on the longitudinal axis of the vehicle during a rear end collision
- Acceleration acting on the lateral axis of the vehicle during a side collision

Moreover, the control module checks
- the switch states of the left front seat belt buckle switch (S68/3) and right front seat belt buckle switch (S68/4),
- the momentary status of the front passenger seat via the electronic evaluation circuitry for the front passenger seat occupied recognition sensor with automatic child seat recognition (B48).

The control module checks all of the signals received and, in the event of a collision, actuates precisely the airbag/side airbag and emergency tension retractors required to provide the best possible protection for the passengers.

An additional safety sensor is integrated into the control module for protection against erroneous actuation during normal driving operation. This sensor, which also has the function of a switch, actuates only in the event of deceleration caused by a head-on collision. It is connected in series with the squib circuits for the driver and passenger airbags and conducts the full triggering current for their actuation.

The safety sensor is not connected into the squib circuits for the driver and passenger emergency tensioning retractors. However its switching status is checked by the control module before actuating the emergency tensioning retractors. The emergency tensioning retractors are actuated only when it has been switched due-to deceleration.

In the event of a side collision the safety sensor has no function. Here additional safety against erroneous actuation is achieved by checking the second (redundant) acceleration sensor.