Seat Belt Control Module: Description and Operation

STRUCTURAL SEAT BELT SYSTEM (WITH SEAT BELT CONTROL TIMER MODULE)

The structural seat with integrated Retractor Integrated Height Adjuster allows the seat belt to comfortably fit a large range of occupants. The seat belts are attached to the seat instead of the body which allows better passenger access to the rear seat.

Since the retractor is mounted to the seat back that can recline, a typical seat belt g-sensor cannot be used in the retractor. Instead, a solenoid inside the retractor is used to lock and unlock the seat belt when electronically signaled by a remote g-sensor. The remote g-sensor is located inside the Seat belt Control Timer Module (SCTM). The SCTM is located under the center console the center console. The seat belt retractor solenoid is located in the seat back and is serviced as an assembly.

When the solenoids are powered, the seat belt can be moved. When the solenoids are not powered, the seat belts can not be extracted. This is necessary to ensure that occupants are always safe, even in the case of a power loss during an accident. Whether the seat belts are in lock or unlock position, an occupant can always release the seat belt and it will retract.

The SCTM controls the seat belt solenoids. It supplies power continuously to the seat belts whenever the ignition is in the RUN or ACCESSORY position. The module has two other unique functions: that of a time and g-sensor.

The SCTM was designed with a timer function so that when the vehicle is not in use, the battery would not be prematurely drained. The module times out after approximately 30 minutes if no inputs are sent to the module. The module will power the seat belts for a period of time when there is an input:
a. from either door ajar switch (open or closed), or
b. the ignition switch is moved from RUN or ACCESSORY to the OFF position.
Each time one of these inputs occurs, the timer is reset to keep the belts powered for 30 minutes.

The g-sensor function of the SCTM will cut power to the seat belts whenever:
a. the vehicle accelerates or decelerates at a rate greater than or equal to 0.7g in any direction, or
b. the vehicle is tilted to an angle greater than or equal to 45°.
Input of ignition switch in the RUN or ACCESSORY position will cause the module to power the seat belts as long as the condition exists.

The SCTM incorporates limited diagnostics. The detectable faults include solenoid short to ground, open or shorted to battery, internal fault, or no acceleration within the past 10 timer cycles. Faults are communicated to the seat belt lamp via a single fault line to the body control module. The body control module communicates the fault on the bus to the cluster/lamp.