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.
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Detachable trailer hitch (accessory)
Detachable trailer hitch (accessory)
a Ball holder
b Locking bolt
c Cotter pin
d Hitch assembly
e Safety wire attachment ...
CD/DVD functions
Center console control panel
1 Disc slot
2 MEDIA button
3 Eject
4 Number keys
5 TUNE:Turn to navigate among menu
selections/folders/tracks.
6 OK/MENU: Press to confirm your selection
or ac ...
Operation
Steering wheel-mounted controls and display
1 Standby mode
2 Resume set speed
3 Deactivating
4 Activate/set speed
5 Set speed indicator (parentheses indicate standby mode) ...
