SEAT BELT SWITCH
DESCRIPTION
The Seat Belt Switch is a Hall Effect-type sensor.
This sensor consists of a fixed-position, Hall Effect
Integrated Circuit (IC) chip and a small permanent
magnet that is integral to the left seat belt buckle.
The left seat belt buckle is located on a stamped steel
stanchion within a molded plastic scabbard and
secured with a screw to the left side of the transmis-
sion tunnel. The seat belt switch is connected to the
vehicle electrical system through a two-lead pigtail
wire and connector on the left seat belt buckle, which
is connected to a wire harness connector in the body
wire harness. A radio noise suppression capacitor is
connected in parallel with the IC where the two pig-
tail wire leads connect to the IC pins.
The seat belt switch cannot be adjusted or repaired
and, if faulty or damaged, the entire left seat belt
buckle must be replaced.
OPERATION
The seat belt switch is designed to provide a status
signal to the seat belt switch sense input of the Occu-
pant Restraint Controller (ORC) indicating whether
the left seat belt is fastened. The ORC uses the seat
belt switch input as a factor in determining what
level of force with which it should deploy the multi-
stage driver and passenger airbags. In addition, the
ORC sends electronic messages to the ElectroMe-
chanical Instrument Cluster (EMIC) to control the
seat belt indicator based upon the status of the left
seat belt switch.
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 (IC) chip within the buckle. The
field of the permanent magnet induces a current
within the chip. The chip provides this induced cur-
rent as an output to the ORC, which monitors the
current to determine the status of the left seat belt.
When the seat belt is unbuckled, the spring-loaded
slide moves upward and shields the IC 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 left
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 EMIC then
store a Diagnostic Trouble Code (DTC) for any fault
that is detected in the seat belt switch circuit. To
properly diagnose the seat belt switch, a DRBIIIt
scan tool and the appropriate Body Diagnostic Proce-
dures manual must be used.
SEAT BELT TENSIONER
DESCRIPTION
Seat belt Tensioners supplement the airbag sys-
tem. The seat belt tensioners are integral to the front
seat belt retractor units, which are secured to the
vehicle frame and are concealed behind the rear
bulkhead trim. The seat belt tensioner consists pri-
marily 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.
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 airbag deployment. The tensioner is a one time
pyrotechnic device. A growling or grinding sound
while attempting to operate the seat belt retractor is
a sure indication that the seat belt tensioner has
been deployed and requires replacement.
OPERATION
The seat belt tensioners are deployed in conjunc-
tion with the 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.
8O - 14 RESTRAINTS ZB
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