Grand Caravan V6-3.3L Flex Fuel (2008)
Seat Belt Tensioner: Description and Operation
Operation
OPERATION
The seat belt retractor tensioners and buckle tensioners are deployed 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.
On the retractor tensioner, the gas generator is installed in one end of the tubular metal piston housing, which contains a piston and a small rack gear. As
the gas expands, it pushes the piston and the rack gear through the tube. The rack gear engages a pinion gear that drives a gear set in the tensioner
housing, which rotates the seat belt retractor spool causing the slack to be removed from the front seat belts.
On the buckle tensioner, the gas generator is installed in one end of the tubular metal piston housing, which contains a piston secured to one end of a
cable. The cable is routed around an integral guide to the buckle, which is secured to the opposite end of the cable. As the gas expands, it pushes the
piston and the cable through the tube and pulls the buckle downward, causing the slack to be removed from the front seat belts.
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 occupants of the front seat might experience in these situations as a result of a harmful contact with
the steering wheel, steering column, instrument panel or windshield. Also, the seat belt retractor has a two-stage mechanism that is designed to control
the loading being applied to the occupants by the seat belts during a frontal impact, further reducing the potential for occupant injuries.
The ORC monitors the condition of the seat belt tensioners through circuit resistance, and will illuminate the airbag indicator in the ElectroMechanical
Instrument Cluster (EMIC) and store a Diagnostic Trouble Code (DTC) for any fault that is detected. Proper diagnosis of the seat belt tensioner gas
generator and squib circuits requires the use of a diagnostic scan tool.
