1. Remove the rear seat cushion.
2. Remove the bolts.

3. Remove the rear buckles.
4. Install in the reverse order of removal.
Front buckle removal/installation
Seat belt inspectionMazda 6 Service Manual: Immobilizer System
The immobilizer system allows the engine to start only with a key the system
recognizes.
If someone attempts to start the engine with an unrecognized key, the engine
will not start, thereby helping to prevent vehicle theft.
If you have a problem with the immobilizer system or the key, consult ...
Mazda 6 Service Manual: Cell Phones
WARNING
Please comply with the legal regulations concerning the use of communication
equipment in vehicles in your country: Use of any electrical devices such
as cell phones, computers, portable radios, vehicle navigation or other devices
by the driver while the vehicle is moving is dangerous ...