Diagnostic procedure
Mazda 6 Service Manual: Scheduled Maintenance (U.S.A., Canada, and Puerto Rico)
Follow Schedule 1 if the vehicle is operated mainly where none of the following
conditions (severe driving conditions) apply.
Repeated short-distance driving
Driving in dusty conditions
Driving with extended use of brakes
Driving in areas where salt or other corrosive materials are used
...
Mazda 6 Service Manual: Cruise Control Function
While this function is operating, the headway control operation is canceled and
only the cruise control function operates.
The vehicle speed can be set more than about 25 km/h (16 mph).
Use the cruise control function on expressways and other highways which do not
require a lot of repeated acc ...