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 AdjusterSpark Plug Inspection [Skyactiv G 2.0]
Specification
Spark plug type
PE01-18110, PE02-18110, PE5R-18110, PE5S-18110
Plug Gap Inspection
CAUTION:
To avoid possible damage to the tip, do not adjust the plug gap.
To prevent damaging the tip, use a wire type plug gap gauge when inspecting
the plug gap.
...
Purge Solenoid Valve Inspection [Mzr 2.0, Mzr 2.5]
Airflow Inspection
1. Remove the battery cover..
2. Disconnect the negative battery cable..
3. Remove the purge solenoid valve..
4. Inspect airflow between the ports under the following conditions.
Measured condition
Continuity between A—B
...
Mass Air Flow (MAF) Sensor/Intake Air Temperature (Iat) Sensor No.1 Removal/Installation
[Skyactiv G 2.0]
CAUTION:
Be careful not to hit the sensor element or allow foreign matter to get on
it during sensor removal/installation. If the sensor element is hit or foreign
matter gets on it, an error may occur in the sensor output signal resulting
in deterioration in the engine control.
...