Seat Belt Systems: Description and Operation

Passive Seat Belt System Functional Operation
The Passive Belt Control Module (PBCM) is an electronic device that controls the right front seat torso belt carrier drive motor.

The torso belt carrier is automatically driven forward when the right front door is opened to facilitate front passenger side entry and exit. The belt carrier is automatically driven rearward when the vehicle is in a normal driving mode (ignition on, right door closed, and torso belt fastened to the carrier), thus providing a passive form of restraint.

The passive belt control module (PBCM) monitors the location of the belt carrier and the functioning of the carrier drive motor when it is in operation.

The PBCM also responds to various input switches (i.e.: door jamb switch, seat belt retractor).

The PBCM provides diagnostic information about the seat belt system through the DRB (diagnostic read-out box) or equivalent scan tool.

Diagnostic Trouble Codes
Passive Seat Belt System - Seat belt diagnostic trouble codes are not stored. They are active only while the ignition is on and can be read using the DRB.

Once the ignition is turned off, any codes that were active will be "forgotten" by the PBCM.
- If the fault still exists when the ignition is turned back on, the code will become active again.
- Since seat belt codes are not stored, they cannot be erased using the DRB.