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:
BRAKE Brake circuit malfunction
The brake system is a hydraulic system consisting
of two master cylinders and two separate
brake circuits. If a problem should occur in
one of these circuits, it is still possible to stop
the vehi ...
Turn signal indicator – trailer (certainmodels)
If you are towing a trailer, this
light
will flash simultaneously with the
turn signals on the trailer. If the
light does not flash when signaling,
neither the trailer's turn signals nor
the ve ...
Fuel filler cap
The fuel filler door, located on the right rear
quarter panel, is connected to your vehicle's
central locking system. ...
