Depress the button on the seat belt buckle.
If the belt does not fully retract, pull it out and check for kinks or twists. Then make sure it remains untwisted as it retracts.

NOTE If a belt does not fully retract, inspect it for kinks and twists. If it is still not retracting properly, have it inspected at an Authorized Mazda Dealer.
Fastening the Seat Belt
Front Shoulder Belt AdjusterBrake Fluid Level Sensor Inspection
1. Disconnect the brake fluid level sensor connector from the master cylinder.
2. Inspect for continuity according to fluid level between the brake fluid level
sensor terminals.
If not as indicated in the table, replace the reserve tank.
...
Manual Transaxle Oil Replacement [C66 M R]
1. Park the vehicle on level ground.
2. Remove the aerodynamic under cover No.2..
3. Remove the drain plug and gasket, and drain the manual transaxle oil.
4. Install a new gasket and the drain plug.
Tightening torque
39—59 N·m {4.0—6.0 kgf·m, 29—43 ft·lbf}
5. Remov ...
Oil Seal (Differential) Replacement [A26 M R]
1. On level ground, jack up the vehicle and support it evenly on safety stands.
2. Drain the oil from the transaxle..
3. Remove the front tires..
4. Remove the splash shield..
5. Remove the aerodynamic under cover No.2..
6. Separate the drive shaft and joint shaft from the transaxle..
7 ...