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:
Under the Hood
The XC70's turbocharged 2.5-liter inline-five-cylinder delivers 208
horsepower and 236 pounds-feet of torque. Volvo's standard Geartronic
five-speed-automatic transmission has a feature that permi ...
Radio text
Some stations transmit information on program content, artists, etc. This information
can be shown on the display.
Activate/deactivate in FM mode under Show radio text. ...
Tread wear indicator
The tires have wear indicator strips running
across or parallel to the tread. The letters TWI
are printed on the side of the tire. When
approximately 1/16" (1.6 mm) is left on the
tread ...
