RESTRAINT SYSTEMS
DESCRIPTION AND OPERATION
13
Seat belt pretensioners
During a frontal collision the seat belt pretensioners
tighten the front seat belts to ensure the occupants
are securely held in their seats. A pretensioner is
integrated into the buckle assembly of each front
seat belt.
The two pretensioners are handed, but otherwise
identical. Each pretensioner has a tube containing
propellant and a piston. The piston is attached to a
steel cable, the opposite end of which is attached to
the seat belt buckle. An igniter (squib) in the base of
tube provides an ignition source when triggered by a
fire signal from the airbag ECU. A fly lead with a 2
pin connector links the igniter to the vehicle wiring.
On receipt of a fire signal from the airbag ECU, the
igniter ignites the propellant. The burning propellant
rapidly produces nitrogen gas that drives the piston
along the tube, pulling on the cable and drawing the
buckle towards the buckle assembly fixing point on
the seat.
SRS warning lamp
The SRS warning lamp provides system status
information for the driver. The lamp consists of a
bulb behind a red SRS graphic at the base of the
tachometer in the instrument pack. The bulb is a
serviceable item that can be renewed from the rear
of the instrument pack.
Seat belt pretensioner components
1. Seat belt buckle
2. Gaiter
3. Steel cable
4. Fixing
5. Igniter
6. Fly lead
7. Vent
8. Tube