SEATBELT CONTROL TIMER MODULE

DESCRIPTION

The Seatbelt Control Timer Module (SCTM) is secured to a bracket underneath the front edge of the front seat center cushion. The SCTM mounting bracket also serves as the support for the slide-out rear seat cup holder unit. 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 jamb switches. The SCTM monitors the external inputs, as well as the inputs from its internal timer and G-sensor. In response to those inputs, the SCTM controls hard wired battery voltage outputs to both electric front seat belt retractor latch solenoids. The SCTM also sends diagnostic outputs to the Airbag Control Module (ACM) over a hard wired fault circuit.
For diagnosis of the CCD data bus, the ACM or the fault circuit input to the ACM from the SCTM, the use of a DRB scan tool and the proper Diagnostic Procedures manual are recommended. The SCTM cannot be adjusted or repaired and, if faulty or damaged, must be replaced.

OPERATION

The SCTM provides battery current to energize the electric seat belt retractor latch solenoids whenever the ignition switch is in the On or Accessory positions, unless the G-sensor input indicates a vehicle condition that requires the seat belt retractor to be latched. When the seat belt retractor latch solenoids are energized the retractor spools are unlatched, and the seat belt webbing can be extracted from the retractor. When the solenoids are de-energized the retractor spools latch, preventing the seat belt webbing from being extracted further from the retractor. This logic ensures that the seat belts will be latched and remain latched if battery power is lost during a vehicle collision.

The electromechanical G-sensor within the SCTM monitors the rate of vehicle acceleration and deceleration in any horizontal direction. The G-sensor also responds to the horizontal attitude of the vehicle. If the G-sensor monitors a gravity force of greater than about 0.7G in any horizontal direction, or that the vehicle is tilted in any direction at an angle of greater than about 45 degrees, the SCTM will sense the input from the G-sensor and de-energize the seat belt retractor latch solenoids.

The SCTM electronic timer circuit provides the vehicle occupants with the ability to extract the seat belt webbing from the retractor spool for a time period of about 30 minutes after the ignition switch is turned to the Off position, unless the G-sensor input indicates a vehicle condition that requires the seat belt retractor to be latched. The electronic timer circuit also monitors the state of the door jamb switches, and unlatches the seat belt retractors after either door jamb switch cycles from open to closed or from closed to open. Each time the SCTM receives an input indicating a change in the state of a monitored switch has occurred, the 30 minute timer starts again. The timer de-energizes the retractor latch solenoids after about 30 minutes to prevent the battery from being drained while the vehicle is not being driven.

The hard wired SCTM fault circuit output to the ACM is used to indicate whether a fault condition is present in the electronic seat belt control system. The ACM continuously monitors the SCTM fault circuit and sends the proper messages to the instrument cluster over the Chrysler Collision Detection (CCD) data bus to turn the seat belt reminder lamp on or off. When no faults are present or monitored by the SCTM, the normal voltage range on the SCTM fault circuit is between one and three volts. If the ACM detects voltages outside the normal range on this circuit, or does not detect any input from the SCTM, it sets a fault code and sends messages to the instrument cluster to turn the seat belt reminder lamp on.