Remove the regulator handle clip using a rag as shown.

Inner handle removal/installation
Regulator handle installationMazda 6 Service Manual: Manually Shifting Down
You can shift gears down by operating the selector lever or the steering shift
switches (some models).
M6 → M5 → M4 → M3 → M2→ M1
Using selector lever
To shift down to a lower gear, tap the selector lever forward (-) once.
Using steering shift switch (Some model ...
Mazda 6 Service Manual: Obd drive mode
Performing the Drive Mode inspects the OBD system for proper operation.
The Drive Mode must be performed to ensure that no additional DTCs are
present.
During Drive Mode, the following systems are inspected:
- Oxygen sensor (HO2S)
- Oxygen sensor heater
- Catalytic converter (TW ...