Mazda 3 2020 Owner's Manual page 180

When Driving
Start/Stop Engine
(European model)

The light flashes when the driver's
door is opened while engine idling is
stopped to notify the driver that
engine idling is stopped. It turns off
when the driver's door is closed.
4-22
*Some models.
Cylinder Deactivation
▼ Cylinder Deactivation
The cylinder deactivation is a function
designed to reduce fuel consumption
and improve fuel economy by
deactivating 2 out of the 4 cylinders
while driving. The function constantly
determines which is better for driving;
4 cylinders or 2 cylinders, regardless of
the driver's operations, and it performs
the switching automatically.
When the cylinder deactivation
function does not operate
The cylinder deactivation function
does not operate under the following
conditions.
The selector lever is in the P, N, or R

position (automatic transmission), or
1st gear (manual transmission).
The engine oil temperature or engine

coolant temperature is low.
After disconnecting the battery

terminals for some reason, such as
for battery replacement.
*