ELECTRIC
SYSTEM
FIAT PUNTO TRAINING OUTLINE
Fiat Auto S.p.A.
After Sales Training
9.7.3 Airbag node (SDM)
It constitutes the “core” of the occupant restraint system and is located on the front tunnel. It
simultaneously controls all the restraint system actuation and detection devices by processing
signals from the various sensors found on the vehicle. It decides on the specific protection
devices are to be actuated in case of accident (and when the same have to be actuated)
through the signals from the sensors it incorporates.
Moreover, it prevents the aforesaid devices from being actuated when a minor collision takes
place. A capacitor (which acts as a power reserve) ensures full operation of the front bags in
the event that no power is supplied by the electric system (i.e. when a collision causes the
battery or the power cables to be broken).
The algorithm used for the head-on collision situations is, in the operators and experts’ jargon,
referred to as “Crash Severity Algorithm” since it can tell whether a collision is serious, so as
to properly actuate the dual-stage airbags.
SDM functions
System fault acquisition.
Transmitting the airbag status signal (ON, OFF, Flash) on the B-CAN line.
Acquiring the airbag warning light status (ON, OFF, Fail) from the B-CAN line through the
warning light itself.
Performing real-time memorization of the airbag warning light status (ON, OFF, Fail) (the
permanent memory for the collisions already occurred is also available).
If an airbag warning light failure occurs, the SDM shall set the passenger’s airbag deactivation
warning light to the ON condition for 4 seconds.
If the test phase is not completed, through the external diagnosis instrument, the drive unit
shall command airbag warning light blinking indefinitely, until the correct command is received
from the external diagnosis equipment.
Acquiring data from the various side and front sensors.
gb Fiat Grande Punto OK
503 / 532
© 2005 Fiat Auto S.p.A. – All rights reserved.
Actuating the various airbags and pretensioners.