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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Getting Around
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The cargo area lighting comes on automatically
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CHECK ENGINE Malfunction indicatorlight
On-Board Diagnostics II (OBDII): As you drive,
a computer called "OBDII" monitors your vehicle's
engine, transmission, electrical and emission
systems. The CHECK ENGINE light will
light ...
