Commander 2WD V8-4.7L (2008)
Seat Belt Tensioner: Description and Operation
Operation
OPERATION
The seat belt tensioners are deployed in conjunction with the dual 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 cylinder tube where the piston that is attached to one end of the buckle cable is sealed to the inside
circumference of the tube. As the gas expands, it pushes the piston down the tube, pulling the cable around the pulley, drawing the buckle downward,
collapsing the scabbard, and removing any excess slack from the seat belt.
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 or windshield. Also, a torsion bar in the seat belt retractor that the retractor spool rides upon is designed to deform in
order 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) (also known as the Cab Compartment Node/CCN) 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. Refer to the appropriate diagnostic
information.
