Seat Belt Systems: Description and Operation

CIRCUIT OPERATION
The purpose of the Passive Restraint Control Module is to allow the vehicle doors to be opened without restriction by the Seat Belts. Without this feature, the Retractor Lock Pendulums would lock the belts as they are pulled out of the retractors when a front door is opened for entry or for exit. This would make it difficult to open the door. To overcome this difficulty, the seat belt locking mechanism is controlled by the Passive Restraint Control Module which controls the operation of the Seat Belt Retractor Release Solenoids.

The Passive Restraint Control Module receives power from the ELEC Fuse. When a door handle switch is operated or a door is open, the associated Door Latch Switch will close. The module will close its output switch and energize all the Seat Belt Solenoids for both doors. The door can then be opened without interference from the Seat Belts. When the door is closed, the Latch Switch opens again and the solenoids are de-energized after about three seconds. The belts are now ready to protect the wearer. To ensure that the solenoids are released, a vehicle speed signal is also supplied to the Module. The Module will release the solenoids any time the vehicle is moving, even if a Latch Switch is closed. If a Latch Switch fails to open and the speed signal causes the solenoids to release, the solenoids cannot be energized again until the switch opens to reset the Module.

IMPORTANT
A shorted Latch Switch will keep the Module from resetting, so both Seat Belts will interfere with door opening. An open Latch Switch will still allow the system to operate properly when the other door is used.