Operation; Seat Belt Tension Reducer; Description - Dodge dakota 2002 Service Manual

8O - 48 RESTRAINTS
SEAT BELT TENSIONER (Continued)
The seat belt tensioner cannot be repaired and, if
faulty or damaged, the entire outboard front seat belt
and retractor unit must be replaced. If the front air-
bags have been deployed, the seat belt tensioners
have also been deployed. The seat belt tensioner is
not intended for reuse and must be replaced follow-
ing a deployment. A locked retractor that will not
allow the seat belt webbing to be retracted or
extracted is a sure indication that the seat belt ten-
sioner has been deployed and requires replacement.
(Refer to 8 - ELECTRICAL/RESTRAINTS/FRONT
OUTBOARD SEAT BELT & RETRACTOR - REMOV-
AL).

OPERATION

The seat belt tensioners are deployed by a signal
generated by the Airbag Control Module (ACM)
through the driver and passenger seat belt tensioner
line 1 and line 2 (or squib) circuits. When the ACM
sends the proper electrical signal to the tensioners,
the electrical energy generates enough heat to ini-
tiate a small pyrotechnic gas generator. The gas gen-
erator is installed at the top of the tensioner housing
which contains a long metal tape that is routed
through two chambers within the housing. Each end
of the tape is wound around the outer sleeve of a
mechanical clutch mechanism secured to one end of
the torsion bar upon which the retractor spool is
secured. As the gas expands, it is directed against
the metal tape within the two chambers of the hous-
ing causing the tape to unwind from the clutch
sleeve. As the clutch rotates it engages the torsion
bar, which drives the seat belt retractor spool causing
the slack to be removed from the seat belt.
Once a seat belt tensioning sequence has been
completed, the forward momentum of the occupant
results in deformation of the torsion bar. As the tor-
sion bar deforms it allows the seat belt webbing to
unwind from the retractor spool, which causes the
metal tape to be wound back onto the clutch sleeve
until it is pulled tight against two cutter blades
within the housing, which immediately cut the metal
tape.
Removing excess slack from the seat belt not only
keeps the occupant 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 a
harmful contact with the steering wheel, steering col-
umn, instrument panel and/or windshield. The tor-
sion bar is designed to deform in order to control the
loading being applied to the occupant by the seat belt
during a frontal impact, further reducing the poten-
tial for occupant injuries.
The ACM monitors the condition of the seat belt
tensioners through circuit resistance. The ACM will
illuminate the airbag indicator in the ElectroMe-
chanical Instrument Cluster (EMIC) and store a
Diagnostic Trouble Code (DTC) for any fault that is
detected. For proper diagnosis of the seat belt ten-
sioners, a DRBIII scan tool is required. Refer to the
appropriate diagnostic information.
SEAT BELT TENSION
REDUCER

DESCRIPTION

Fig. 45 Seat Belt Tension Reducer
1 - TENSIONER HOUSING OR CHAMBER
2 - GAS GENERATOR
3 - TENSIONER PIGTAIL WIRE
4 - SPOOL
5 - TENSION REDUCER (DRIVER SIDE ON STANDARD CAB
ONLY)
6 - REDUCER CONNECTOR RECEPTACLE
A seat belt tension reducer is standard equipment
for the driver side front outboard seat belt on stan-
dard cab versions of this model (Fig. 45). The tension
reducer is integral to the driver side front outboard
seat belt and retractor unit, which is secured to the
inner B-pillar on the left side of the vehicle. The
retractor is concealed beneath the molded plastic
inner B-pillar trim. The seat belt tension reducer
consists primarily of a 12-volt Direct Current (DC)
solenoid and an integral connector receptacle that is
located on the forward facing end housing of the
retractor. The seat belt tension reducer is controlled
by a battery current output of the ignition switch and
a ground path provided by the seat belt switch, and
is connected to the vehicle electrical system through
a dedicated take out of the body wire harness by a
keyed and latching molded plastic connector insula-
tor to ensure a secure connection.
The seat belt tension reducer cannot be repaired
and, if faulty or damaged, the entire driver side front
DR