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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Operation and function
LDW can be switched on or off by pressing the
button on the center console. A light in the button
illuminates when the function is on.
The trip computer display shows Lane Depart
Warn Standby ...
Symbols and messages in the display
...
Oil specifications
Engine oil must meet the minimum ILSAC
specification GF-4, API SL, or ACEA A1/B1.
Lower quality oils may not offer the same fuel
economy, engine performance, or engine protection.
Depending on ...
