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:
Glove compartment
The owner's manual and maps can be kept
here. There are also holders for pens and fuel
cards. The glove compartment can be locked
manually with the key blade, see page 67. ...
Extra high beam
1. Remove the headlight housing from the
vehicle (see page 322).
2. Remove the cover over the bulbs (see
page 323).
3. Disconnect the wiring connector from the
bulb holder.
4. Remove the bu ...
What is an Onboard Diagnostic System (OBD II)?
OBD II is part of your vehicle's computerized
engine management system. It stores diagnostic
information about your vehicle's emission
controls. It can light the Check Engine light
(MIL) if it ...
