Audi R8 2008 Service Training Manual page 16

Occupant Protection
Airbag Control Module J234
The electronics integrated into the Airbag Control Module
detect and evaluate vehicle acceleration and deceleration
in order to identify a vehicle collision. In addition
to internal sensors in the control module, external
sensors are also used to detect vehicle acceleration and
deceleration during a collision.
J234 recognizes a collision only from the information
provided by the sensors, deciding when and which safety
components to activate once all sensor information has
been evaluated. Front, side and rear impact collisions can
be recognized by J234.
Another purpose of J234 is to activate the corresponding
restraint systems (safety belt tensioner or safety belt
tensioner and airbag), depending on the type and
severity of the impact, and to report the crash event to
other vehicle systems.
J234 has the following main tasks:
– Crash Recognition (Front, Side, Rear).
– Defined Triggering of Safety Belt Tensioners, Airbags
and Battery Interrupt.
2
– Defined Triggering of the Second Front Airbag Stage.
– Evaluation of All Input Information.
– Continuous Monitoring of the Entire Airbag System.
– Independent Power Supply with a Capacitor for a
Defined Period of Time (Approximately 50 ms).
– Fault Display by a Failure Warning Lamp.
– Reporting of a Crash Event to Other System
Components through the Powertrain CAN-Bus or
Discrete Crash Output (Conventional Wiring).
– Activation of the Safety Belt Warning Lamp.
For information on which components must be replaced
after an accident, please refer to the appropriate repair
manual.
J234 can only be replaced using a VAS scan tool with
online capabilities, using the Guided Fault Finding or
Guided Functions.
J234 must be coded and adapted according to the
respective vehicle. If the coding and/or adaptation is not
performed properly, malfunctions could occur in other
vehicle systems, for example, in the ESP.