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: Floor Mat
We recommend the use of Genuine Mazda floor mats.
WARNING
Make sure the floor mats are hooked on the retention pins to prevent them
from bunching up under the foot pedals: Using a floor mat that is not secured
is dangerous as it will interfere with the accelerator and brake pedal operation,
...
Mazda 6 Service Manual: No. 2 all on-board diagnostic functions inoperative
When performing an asterisked (*) troubleshooting inspection, shake the
wiring harness and connectors while doing the inspection to discover whether
poor contact points are the cause of any intermittent malfunctions. If there
is a problem, check to make sure connectors, terminals and wir ...