uses the seat belt switch input to determine the sta-
tus of the driver side front seat belt. The ORC then
sends electronic messages to the Instrument Cluster
to control the seat belt indicator based upon the sta-
tus of the seat belt switch input.
A spring-loaded slide with a small window-like
opening is integral to the buckle latch mechanism.
When a seat belt tip-half is inserted and latched into
the seat belt buckle, the slide is pushed downward
and the window of the slide exposes the Hall Effect
Integrated Circuit chip within the buckle. The field
of the permanent magnet induces a current within
the chip. The chip provides this induced current as
an output to the ORC, which monitors the current to
determine the status of the driver side front seat
belt. When the seat belt is unbuckled, the spring-
loaded slide moves upward and shields the Inte-
grated Circuit from the field of the permanent
magnet, causing the output current from the seat
belt switch to be reduced.
The seat belt switch receives a supply current from
the ORC, and the ORC senses the status of the
driver side front seat belt through its pigtail wire
connection to the airbag overlay wire harness. The
ORC also monitors the condition of the seat belt
switch circuit and will illuminate the airbag indicator
in the cluster then store a Diagnostic Trouble Code
(DTC) for any fault that is detected in the seat belt
switch circuit. For proper diagnosis of the seat belt
switch, a DRBIII
t scan tool is required and the
appropriate Body Diagnostic Procedures manual.
SEAT BELT TENSIONER
DESCRIPTION
Seat Belt Tensioners supplement the dual front air-
bags. The seat belt tensioners are integral to the
front seat belt retractors, which are secured to the
inner B-pillar on the right and left sides of the vehi-
cle. The retractor is concealed beneath the lower
B-pillar trim. The seat belt tensioner consists prima-
rily of a sprocket/pinion, a steel tube, a cast metal
housing, numerous steel balls, a stamped metal ball
trap, a torsion bar, a small pyrotechnically activated
gas generator, and a short pigtail wire. All of these
components are located on one side of the retractor
spool on the outside of the retractor housing except
for the torsion bar, which serves as the spindle upon
which the retractor spool rides. The seat belt tension-
ers are controlled by the Occupant Restraint Control-
ler (ORC) and are connected to the vehicle electrical
system through a dedicated take out of the body wire
harness by a keyed and latching yellow molded plas-
tic connector insulator to ensure a secure connection.
The seat belt tensioners cannot be repaired and, if
faulty or damaged, the entire front seat belt and
retractor unit must be replaced. If the front airbags
have been deployed, the seat belt tensioners have
also been deployed. The seat belt tensioners are not
intended for reuse and must be replaced following
any front airbag deployment. A growling or grinding
sound while attempting to operate the seat belt
retractor is a sure indication that the seat belt ten-
sioner has been deployed and requires replacement.
Refer to the proper Body Diagnostic Procedures man-
ual for diagnosis and testing.
OPERATION
The seat belt tensioners are deployed in conjunc-
tion with the front airbags by a signal generated by
the Occupant Restraint Controller (ORC) through the
driver or passenger seat belt tensioner line 1 and line
2 (or squib) circuits. When the ORC sends the proper
electrical signal to the tensioners, the electrical
energy generates enough heat to initiate a small
pyrotechnic gas generator. The gas generator is
installed in one end of a steel tube that contains
numerous steel balls. As the gas expands, it pushes
the steel balls through the tube into a cast metal
housing, where a ball guide directs the balls into
engagement with the teeth of a sprocket that is
geared to one end of the retractor spool. As the balls
drive past the sprocket, the sprocket turns and drives
the seat belt retractor spool causing the slack to be
removed from the front seat belts. The ball trap cap-
tures the balls as they leave the sprocket and are
expelled from the housing.
Removing excess slack from the front seat belts not
only keeps the occupants properly positioned for an
airbag deployment following a frontal impact of the
vehicle, but also helps to reduce injuries that the
occupant might experience in these situations as a
result of harmful contact with the steering wheel,
steering column, instrument panel and/or windshield.
Also, the seat belt tensioner torsion bar that the
retractor spool rides upon is designed to deform in
order to control the loading being applied to the occu-
pants by the seat belts during a frontal impact, fur-
ther reducing the potential for occupant injuries.
The ORC monitors the condition of the seat belt
tensioners through circuit resistance, and will illumi-
nate the airbag indicator in the instrument cluster
and store a Diagnostic Trouble Code (DTC) for any
fault that is detected. For proper diagnosis of the
seat belt tensioners, a DRBIII
t scan tool is required
and the appropriate Body Diagnostic Procedures
manual.
CS
RESTRAINTS
8O - 45
SEAT BELT SWITCH (Continued)