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: Active Adaptive Shift (AAS)
Active Adaptive Shift (AAS) automatically controls the transaxle shift points
to best suit the road conditions and driver input. This improves driving feel. The
transaxle may switch to AAS mode when driving up and down slopes, cornering, driving
at high elevations, or depressing the accelerato ...
Mazda 6 Owners Manual: Oil pressure switch removal/installation
Warning
When the transaxle and ATF are hot, they can badly burn. Turn off
the engine and wait untill they are cool before replacing ATF.
1. Disconnect the negative battery cable.
2. Remove the under cover.
3. Disconnect the cord assembly connector.
4. Remove the oil pressure switch.
...