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 AdjusterMazda 6 Owners Manual: Vehicle speedometer sensor (vss) inspection
Visual Inspection
1. Remove the VSS. (See VEHICLE SPEEDOMETER SENSOR (VSS)
REMOVAL/INSTALLATION.)
2. Make sure that the sensor is free of any metallic shavings or particles.
If any are found on the sensor, clean them off.
3. Install the VSS. (See VEHICLE SPEEDOMETER SENSOR (VSS)
REMOVAL ...
Mazda 6 Owners Manual: Clutch master cylinder disassembly/assembly
1. Disassemble in the order indicated in the table.
2. Assemble in the reverse order of disassembly.
Snap Ring Disassembly/Assembly Note
Hold the piston down using a cloth-wrapped pin punch.
If disassembling, remove the snap ring; if assembling, install it.
...