Faults can be recorded and not show up with an engine light being shown
engine lights generally are reserved for the more serious faults that will cause damage to the engine and / or transmission
minor out of parameter faults of sensors are stored for a code reading
It is best when asking a question , that you give all the details like make and model, year , problems causing a necessity to read the faults
for example just plugging in a scanner in a nissan will not get any codes unless the switch in the side of the ECM is activated

OBD wont show errors unless the check engine light is on.