_GM Seatbelt Restraint System

Description and Operation

Seat belts are the primary means of occupant restraint.  Seat belts help to keep occupants inside the passenger compartment and to gradually reduce the impact forces.  All seat belt retractors have emergency locks. The retractors remain unlocked during normal operation and under normal driving conditions. The retractors remain unlocked during normal conditions in order to allow free movement of the upper body of each occupant.  A pendulum locks the seat belt webbing into position. The pendulum causes a locking bar to engage a cog on the spool of the retractor mechanism when the following conditions occur:

• A rapid extraction of the seat belt webbing from the retractor
• An abrupt change in the vehicle speed
• An abrupt change in the vehicle direction
• Operation of the vehicle on a steep upgrade
• Operation of the vehicle on a steep downgrade

The seat belts, except for the driver seat belt, have an automatic locking feature, or a cinch feature. The cinch feature is recommended for securing a child seat. The cinch feature is engaged by fully extending the seat belt from the retractor. Once engaged, the seat belt can retract, but cannot be extended again until the cinch feature is cancelled. The cinch feature is cancelled when the seat belt has fully retracted. This vehicle is also equipped with a supplemental inflatable restraint (SIR) system. Refer to Supplemental Inflatable Restraint System Description and Operation for a description of the seat belt retractor pretensioner.

Front Seat Belt System

The front seat belt system includes the following components:

• The driver and passenger seat belt buckles, attached to the inboard side of the seat frame
• The driver and passenger seat belt retractor pretensioners
• The driver and passenger seat belt switch located in the seat belt buckles

Seat Belt System Circuit Description

There is only one fasten safety belt indicators for this vehicle. The driver fasten safety belt indicator is located on the instrument panel cluster (IPC).  The passenger fasten safety belt indicator does not exist.  The driver's indicator is controlled by the IPC at the request of the inflatable restraint sensing and diagnostic module (SDM). The driver indicator, when initiated, will illuminate for 20 seconds followed by 55 seconds of flashing. Audible warnings will initiate simultaneously with visual warnings and last for 8 seconds. Subsequently, similar events will occur until the seat belt is buckled or the ignition is returned to the OFF position.

The driver fasten safety belt indicator will illuminate when any of the following occur:

• The driver seat belt is unbuckled while the ignition is ON.
• The driver seat belt remains unbuckled and vehicle speed is greater than 8 km/h (5 mph).
• Three minutes after previous seat belt status reminder event.
• The IPC performs the displays test at the start of each ignition cycle.

Schematic

Seat Belt Pretensioners (Buckle)

The driver's seat belt pretensioners (and passenger if equipped) consist of a housing, seat belt buckle (pretensioner), seat belt webbing, an initiator, and a canister of gas generating materials.  To view the locations of the seat belt pretentioners refer to Master Electrical Component List. The initiator is part of the seat belt pretensioner deployment loop. When the vehicle is involved in a collision of sufficient force, the Inflatable Restraint Sensing and Diagnostic Module causes current to flow through the seat belt deployment loops to the initiator. Current passing through the initiator ignites the material in the canister producing a rapid generation of gas. The gas produced from this reaction deploys the seat belt pretensioners which removes all of the slack in the seat belts. Depending on the severity of the collision, the seat belt pretensioners may deploy without the front air bags deploying, or they will deploy immediately before the front air bags deploy. A shorting bar (if equipped) is located in the connector.