Stratus Sedan V6-2.7L VIN T FFV (2003)
Seat Belt Control Module: Description and Operation
SEAT BELT CONTROL TIMER MODULE
The Seat Belt Control Timer Module (SCTM) is located below the drivers seat underneath the floor carpeting. It is a black plastic box, containing
electronics for the Structural Seat Belt System.
The SCTM contains an electromechanical Gravity (G)-sensor and an electronic timer circuit. The SCTM receives hard wired external inputs from the
ignition switch and both door ajar switches. The SCTM monitors the external inputs, as well as the inputs from its internal timer and G-sensor. In
response to those inputs from its internal, the SCTM controls hard wired battery voltage outputs to both electric front seat belt retractor latch solenoids.
This belt system attaches to a reclinable seat back so the traditional locking pendulum mechanism would not provide security. A solenoid was designed
to lock the belt and was made part of each of the retractor mechanisms to each seat back. An impact sensor deactivates the solenoids. The impact sensor
is a component of the Seat Belt Control Timer Module (SCTM) located under the drivers seat.
The G-Sensor is sensitive to frontal impact and to a roll or pitch more than 45 degrees and to acceleration or deceleration equal to or greater than 0.7 G's
in any direction.
Since the retractor is mounted on a 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 electrically signaled by a g-sensor. The seat belt retractor solenoid is located in the seat back and is
serviced with the seat back, as an assembly.
When the solenoids are powered, the seat belt can be moved. When the solenoids are not powered, the seat belts cannot 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 power to the seat belt solenoids. It supplies power continuously to the seat belts whenever the ignition key is in the RUN or
ACCESSORY position. The module has two other unique functions that of a timer and a 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 set period of time there is an input
from:
-
Either door ajar switch (open or closed).
-
Ignition switch moved from RUN or ACCESSORY to the OFF position.
Each time one of these inputs occur, 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 belt whenever:
-
The vehicle accelerates or decelerates at a rate greater than or equal to 0.7 G's in any direction.
-
The vehicle is tilted to an angle greater than or equal to 45 degrees.
Input of the 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 shorted to ground.
-
Solenoid open.
-
Solenoid shorted to battery.
-
Internal fault.
-
No acceleration within the last 10 timer cycles. Faults are communicated to the seat belt lamp via a single fault line to the Body Control Module
(BCM). The BCM communicates the fault on the bus to the cluster lamp.
