Mazda 6 Owner's Manual page 322

When Driving
i-ACTIVSENSE
NOTE
If the vehicle speed decreases by
about 15 km/h (9.4 mph) or more
than the set speed, the cruise control
function may be cancelled.
When the vehicle speed is less than
21 km/h (13 mph), the cruise control
function is cancelled. In this case, the
vehicle speed will not return to the
original set speed even if the vehicle
is accelerated to 25 km/h (16 mph) or
higher and the RES switch is pressed.
Reset the cruise control function.
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