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Air bags and seat belt pretensioners
88
OPERATION OF SIDE AIR BAGS
When the ignition is switched on, the control war-
ning light for these air bag and pretensioner sys-
tems is illuminated for several seconds and then is
extinguished.
The air bag and pretensioner system computer is
then on standby as are the side air bags impact
sensors located in the two inner sills of the vehicle.
In the event of a side impact of sufficient force,
the side impact sensor on the impact side sends a
signal to the air bag and pretensioner system
computer , after having had confirmation of an
impact from the electronic safety sensor (incorpo-
rated in the unit).
The unit triggers the ignition of the pyrotechnic
gas generators in the seat which inflate the air
bag cushion (on the impact side).
The side air bags are not triggered during:
- a frontal impact,
- a rear impact,
- an impact on the opposite side.
When triggered, a pyrotechnic gas generator pro-
duces an explosion and a small amount of smoke.
NOTE :the computer and ignition modules supply
normally comes from the vehicle battery.
However, an energy reserve is included in the
computer in case the battery is disconnected at
the start of the impact.
REMINDER : for vehicles fitted with self contained
air bags, see Technical Note 3064A.
COMPUTER
Two types of computer are assembled on these ve-
hicles according to their equipment :
• A unit supplied by a 30 track yellow connector
for vehicles without side air bags. This must be
configured according to the vehicle’s equip-
ment (see configuration).
• A unit supplied by a 50 track orange connector
for vehicles with side air bags.
These units comprise :
- two electronic decelerometers for front air bags
and pretensioners,
- an electronic safety sensor for non-self contai-
ned side air bags (unit with 50 track orange
connector only),
- connections with side electronic sensors in the
inner sills (unit with 50 track orange connector
only),
- an ignition circuit for the different pyrotechnic
systems ,
- an energy reserve,
- a fault finding circuit with memorisation of the
faults detected,
- a control circuit for the warning light on the ins-
trument panel,
- a communication interface K - L via the fault fin-
ding socket.
IMPORTANT
Before removing the computer, it must be locked
using one of the fault finding tools (
XR25, NXR or
OPTIMA 5800).
When this operation is activated,all the ignition
lines are inhibited and the air bag warning light on
the instrument panel is illuminated (new computers
are delivered in this condition).
See following procedure.
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