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: Front/rear abs wheel-speed sensor inspection
Visual Inspection
Remove the wheel and tire, and inspect the sensor for looseness and damage.
Replace the sensor if necessary.
Clearance Inspection
Inspect the clearance between the wheel-speed sensor and the sensor rotor.
Clearance
0.3-1.1 mm {0.012-0.043 in}
Resistance Inspection
...
Mazda 6 Owners Manual: Variable tumble control solenoid valve inspection
1. Remove the variable tumble control solenoid valve. (See INTAKE-AIR SYSTEM
REMOVAL/INSTALLATION.)
2. Inspect airflow between the ports under the following conditions.
If not as specified, replace the variable tumble control solenoid valve.
If as specified, carry out the Circuit Open/Short ...