Seat Belt Tensioner - Dodge Dakota Sport 2001 Service Manual

AN
SEAT BELT SWITCH (Continued)
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, SEAT BELT TENSIONER, OR INSTRU-
MENT PANEL COMPONENT DIAGNOSIS OR SER-
VICE. DISCONNECT AND ISOLATE THE BATTERY
NEGATIVE (GROUND) CABLE, THEN WAIT TWO
MINUTES FOR THE AIRBAG SYSTEM CAPACITOR
TO DISCHARGE BEFORE PERFORMING FURTHER
DIAGNOSIS OR SERVICE. THIS IS THE ONLY SURE
WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE
TO TAKE THE PROPER PRECAUTIONS COULD
RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT
AND POSSIBLE PERSONAL INJURY.
(1) Disconnect and isolate the battery negative
cable. Disconnect the body wire harness connector for
the seat belt switch from the seat belt switch pigtail
wire connector from the driver side front seat belt
retractor. Check for continuity between the ground
circuit cavity of the body wire harness connector for
the seat belt switch and a good ground. There should
be continuity. If OK, go to Step 2. If not OK, repair
the open ground circuit to ground (G307) as required.
(2) Check for continuity between the two cavities
in the seat belt switch pigtail wire connector. There
should be no continuity with the seat belt webbing
retracted, and continuity with the seat belt webbing
pulled out of the retractor far enough to engage the
seat belt buckle. If OK, go to Step 3. If not OK,
replace the faulty driver side front seat belt and
retractor unit.
(3) Remove the instrument cluster from the instru-
ment panel. Check for continuity between the seat
belt switch sense circuit cavity of the body wire har-
ness connector for the seat belt switch and a good
ground. There should be no continuity. If OK, go to
Step 4. If not OK, repair the shorted seat belt switch
sense circuit between the seat belt switch and the
instrument cluster as required.
(4) Check for continuity between the seat belt
switch sense circuit cavities of the instrument panel
wire harness connector (Connector C2) for the instru-
ment cluster and the body wire harness connector for
the seat belt switch. There should be continuity. If
OK, proceed to the diagnosis for the instrument clus-
ter. (Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). If not OK,
repair the open seat belt switch sense circuit between
the seat belt switch and the instrument cluster as
required.

SEAT BELT TENSIONER

DESCRIPTION
Seat belt tensioners supplement the airbag system
for all quad cab versions of this model. The seat belt
tensioners are integral to the front seat belt retrac-
tors, which are secured within each B-pillar in the
vehicle where they are concealed behind the B-pillar
trim. The seat belt tensioner consists primarily 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 com-
ponents 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 tensioners are
controlled by the Airbag Control Module (ACM) and
are 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 tensioners cannot be repaired and, if
faulty or damaged, the entire front seat belt, retrac-
tor, and tensioner unit must be replaced. The seat
belt tensioners are not intended for reuse, and both
tensioners must be replaced following any airbag
deployment. 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. For seat belt ten-
sioner service procedures, (Refer to 8 - ELECTRI-
CAL/RESTRAINTS/FRONT
RETRACTOR - REMOVAL).
OPERATION
The seat belt tensioners are deployed in conjunc-
tion with the airbags by a signal generated by the
Airbag Control Module (ACM) through the driver or
passenger seat belt tensioner line 1 and line 2 (or
squib) circuits. When the ACM sends the proper elec-
trical signal to the tensioner, 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 captures 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
RESTRAINTS 8O - 31
SEAT BELT &