General Information

DESCRIPTION
A structural seat using an electronic seat belt control system is standard factory-installed safety equipment on all extended cab (club cab and quad cab) versions of this model. Refer to the owner's manual in the vehicle glove box for more information on the features, use and operation of all of the factory-installed passenger restraints, including the seat belt system for the structural seat.

The electronic seat belt control system consists of the following components:
- Airbag Control Module (ACM)
- Door jamb switches (one for each front door)
- Ignition switch
- Seatbelt Control Timer Module (SCTM)
- Seat belt reminder lamp
- Seat belt retractor latch solenoids (one for each front outboard seating position)
- Wire harness and connections.

Complete service information for the other seat belt control system components can be located as follows:
- Refer to Airbag Control Module in the Airbag Systems for complete service information for the ACM.
- Refer to Door Jamb Switch in the Vehicle Theft/Security Systems for complete service information for the door jamb switches.
- Refer to Ignition Switch and Key Lock Cylinder in the Ignition System for complete service information for the ignition switch.
- Refer to Instrument Cluster in the Instrument Panel Systems for complete service information for the seat belt reminder lamp.

See the proper Diagnostic Procedures to test or diagnose a problem with the ACM.

OPERATION
In the structural seat system, the driver and passenger side seat belts, seat belt retractors and seat belt height adjusters are integral to the seat back frame. Because the seat belts are anchored to the seat back instead of the vehicle body in the structural seat system easier access is provided to the rear seating area of the vehicle.

However, because the structural seat system has the seat belt and retractor anchored to a movable reclining seat back frame, a typical inertia-type retractor latch mechanism cannot provide the security and accuracy needed to latch the seat belt retractor spool upon a vehicle impact. An electronic seat belt control system was developed to replace the mechanical inertia latch mechanism on models equipped with the structural seat system.

The SCTM controls battery voltage to energize and de-energize the electric solenoids located in the seat belt retractors to control the latching and unlatching of the seat belt retractor spools. The SCTM monitors external inputs from the door jamb switches and the ignition switch, as well as internal inputs from an electronic timer circuit and an electromechanical Gravity (G)-sensor. The SCTM uses these inputs to determine when to latch and unlatch the seat belt retractors.

A seat belt reminder lamp in the instrument cluster lights for about seven seconds each time the ignition switch is turned to the On or Start positions as a reminder to fasten the seat belts. Following the normal seat belt reminder function, the seat belt reminder lamp is turned on or off by the ACM to indicate the status of the electronic seat belt control system. If the seat belt reminder lamp comes on at any time other than during the reminder function, it indicates that there is a problem in the seat belt control system circuits. Such a problem may cause the seat belt retractors not to latch when required.

The seat belt control system also has a test mode feature. This feature allows the seat belt control system to be tested for proper operation while the vehicle is stationary by overriding the normal SCTM control functions. The seat belt control system must be tested for proper operation following the service of any seat belt control system or airbag system component. Refer to Seat Belt Control System Test Mode in the Diagnosis and Testing for more information.