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80 Body
9-5
Front impact sensor
The front impact sensor is used to detect collision
forces at an early stage and send information to
the control module.
The system has two front impact sensors. They
are located on the bumper rail at the same height
as the detachable grille on the front of the car.
The two sensors are identical and both have two
leads connected to them, one for the power
supply and one for transmitting the signal to the
control module.
The sensor contains an acceleration sensor and
a communication circuit. It sends digital
information containing status messages for
diagnosis and acceleration values from 0-127 g
on a lead to the control module. Calculations
concerning the igniter and whether it should be
activated are made in the control module. In case
of a fault in the front impact sensor, the airbags
will still inflate, but somewhat later than would
otherwise be the case.
The front impact sensors communicate by
modulating the continuous power supply from the
airbag control module, which means that the
sensors draw more or less current. These
changes are detected by the microprocessor in
the control module.
Side impact sensor
The pressure from the side impact sensors is
compared by the control module with the lateral
value from the accelerometer before it activates
the side airbag. This is the same side impact
sensor used previously, but the control unit has
new software.
Seat-belt buckle sensor
This sensor is used to detect whether the seat-
belt buckle is locked or not. Using information
from the seat-belt buckle sensors and the seat
position sensors, the control module will be able
to decide how the ignition circuits for the belt
tensioners and the front airbags should be
activated.
Seat position sensor
The seat position sensors are used to detect
whether the seat is in a forward position, i.e. less
than 30% away from the front position, or in a
rear position, i.e. more than 30% or approx.
65mm (2.56in) from the front position of the seat.
Using this information from the seat position
sensor, the control module will be able to
determine how to activate the ignition circuits.
See control module information, p.77.
The seat position sensors are mounted on
manual seats as well as electrically adjustable
seats.