How do states use OBD II for emission inspections?

Many states connect a computer directly to a vehicle's OBD II system. The inspector can then read "faults." In some states, this type of inspection has replaced the tailpipe emission test.
See also:
Symbols in the instrument panel
WARNING
If and
come on at the same time
and the brake level is below the MIN mark
in the reservoir or if a brake system-related
message is shown in the information display: DO NOT DRIVE. ...
Engine and cooling system
Under special conditions, for example when
driving in hilly terrain, extreme heat or with
heavy loads, there is a risk that the engine and
cooling system will overheat. Proceed as follows
to a ...
Changing wheels
Jack location ...
