The High Beam Control System (HBC) operates to switch the headlights automatically between high and low beams after the ignition is switched ON and the headlight switch is in the AUTO and high beam position.
The High Beam Control System (HBC) determines that it is dark based on the brightness of the surrounding area. At the same time, the High Beam Control System (HBC) indicator light (green) in the instrument cluster illuminates.

NOTE
When the vehicle speed is less than about 20 km/h (12 mph), the High Beam Control System (HBC) switches the headlights to low beams.
High Beam Control System (HBC) (Some models)
Manual SwitchingMazda 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: Dynamic Stability Control (DSC)
The Dynamic Stability Control (DSC) automatically controls braking and engine
torque in conjunction with systems such as ABS and TCS to help control side slip
when driving on slippery surfaces, or during sudden or evasive maneuvering, enhancing
vehicle safety.
Refer to ABS and TCS.
DSC opera ...