Audi A8 2019 Service Training page 61

Event Data Recorder (EDR)
The 2019 Audi A8 is equipped with an Event Data Recorder
(EDR).
The EDR is integrated in the Airbag Control Module J234 as
a software module. The task of the EDR is to record relevant
vehicle data over a period of a few seconds in the event of
minor accidents or severe accidents and/or near-accident
events. J234 groups minor accidents or severe accidents
and/or near-accident events into two basic categories.
Category 1: A minor accident has occurred if the airbag
control module has detected an accident in which no pyro-
technic components have deployed.
A near-accident event is a critical driving situation involving
corrective inputs by Audi pre sense and in which no actual
accident occurs.
Note: The airbag control module will normally classify a minor
parking collision as a minor accident because it has a low severity
level.
Category 2: A severe accident is a situation in which pyro-
technic components of the restraint systems, for example,
airbags deploy.
Examples
1. A vehicle has been involved in six minor accidents and/or
near-accident events. Each of these situations has been
recorded in a block. Now a severe accident occurs. The
airbag control module can still be used in this case
because the severe accident overwrites the oldest minor
accident or near-accident event. The control module
therefore meets the condition that at least two of the six
blocks still have to be usable. Note here that minor
accidents and near-accident events can be overwitten by
severe accidents.
2. A vehicle has been involved in four severe accidents. Each
of these accidents has been recorded in a block. Now a
minor accident or near-accident event occurs. The minor
accident or near-accident event is recorded in a separate
block. The airbag control module can still be used because
a free block is still available and the block in which the
minor accident or near-accident event is recorded can be
overwritten by a severe accident. Even if four severe
accidents and two minor accidents or near-accident events
have been stored in the six blocks, the two blocks in which
the minor accidents or near-accident events are recorded
can be overwritten. The control module therefore meets
the condition that at least two of the six blocks still have
to be usable and can still be used.
The recorded data is written to a ring memory. This ring
memory continuously records the last five seconds of
vehicle data while driving. Data which is older than five
seconds is either actively cleared again or overwritten by
new data. If J234 detects an accident, the data recorded
approximately five seconds before and approximately
300 milliseconds after the accident is transferred to non-
erasable read-only memory. This memory has the capacity
to record up to six accident events. Six blocks are available
in the read-only memory module for this purpose.
When J234 detects severe or minor accidents or near-acci-
dent events, the relevant data is successively written to one
of the six blocks of the read-only memory. This means that
each data packet related to an accident or a near-accident
event can be assigned clearly to a block of the memory. A
special feature of this system is that a block can be used by
data related to a minor accident or a near-accident event,
but can be overwritten in the event of a severe accident. In
this case, the oldest minor accident or near-accident event is
overwritten. At least two of the six blocks must still be
usable. If this is no longer the case, Airbag Control Module
J234 must be replaced. Because minor accidents and near-
accident events can be overwritten, they do not necessitate
replacing the airbag control module.
L1
L2
L3
L4
L5
L6
S1
S2
S3
S4
Free
block
Free
block
S1
L2
L3
L4
L5
L6
662_021
S1
S2
S3
S4
L1
Free
block
662_022
57