Contacts for Further Information
Phoenix Vehicle Emissions
600 N. 40th St.
Phoenix, AZ 85008
Tucson Vehicle Emissions
4040 E. 29th St.
Tucson, AZ 85711
ADEQ Air Quality Division
1110 W. Washington St.
Phoenix, AZ 85007
(800) 234-5677 Ext: 771-2308
(602) 771-4829 (Hearing impaired)
Web site: www.azdeq.gov
Updated July 2009
Publication No. C 08-05
printed on recycled paper
This is much quicker and more effective
than the traditional “tailpipe” test. Arizona
is equipping most emissions inspection
stations with OBD-only lanes to take
advantage of this more efficient testing.
Are repairs covered by warranty?
Warranty coverage varies, depending on
the specific failure. However, the federal
Clean Air Act requires that major emissions
control components such as the catalytic
converter be warranted for eight years or
80,000 miles and most emissions-control
components are covered for at least two
years or 24,000 miles.
This technology is built into all 1996 and
newer light-duty cars and trucks.
Commonly known as OBD, the computer-based
system monitors the performance of
many of the engine’s major components,
including individual emission controls.
The system provides owners with an early
warning of malfunctions by way of a dash-board
“Check Engine” light (also known as
a Malfunction Indicator Light or MIL). By
giving vehicle owners this early warning,
OBD protects not only the environment but
also consumers, identifying minor problems
before they become major repair bills.
How does it work?
The OBD system is integral to the computer
system within the vehicle. The OBD system
is connected to and monitors the principal
components of the emissions control system,
as well as several of the engine’s operating
systems or components. When the vehicle
begins to operate outside of predetermined
conditions -- elevated emissions or engine
overheat for example -- the OBD system
first tries to compensate for the problem. If
that doesn’t work, the system illuminates the
MIL light to alert the driver, while storing the
information about the problem. The driver
can then have the problem checked out by
a service technician before there is a break-down
or a more costly component failure.
Can I tell if it is working?
When you turn on the ignition, the “Check
Engine” or “Service Engine Soon” light
should flash briefly, indicating that the
system is active. After this brief flash, the
light should stay off while you drive as long
as no problems are detected. If it stays off,
you can be assured that your vehicle is
being monitored by an early warning sys-tem
that could save you time, money and
fuel while protecting the environment.
What should I do if the light
If the light comes on and stays on, the OBD
system has detected a problem. Your vehicle
might have a condition that wastes fuel,
shortens engine life, or causes excessive air
pollution. If left unaddressed, these
conditions could also damage your vehicle
and lead to increasingly expensive repairs.
For example, OBD can identify a loose or
missing gas cap (which wastes fuel and
contributes to smog) or an engine misfire
(which can lead to severe or permanent
engine damage). If your “Check Engine”
light comes on, don’t panic. The vehicle is
telling you to seek attention soon. When
you reach your destination, make sure the
gas cap is not loose or missing. Always turn
off your engine when refueling. If the light
does not go out after a few short trips
following gas cap replacement or tightening,
have your vehicle serviced by a qualified
What if the light is blinking?
If the light is blinking, a severe engine
problem is occurring, such as a misfire, which
could cause engine and catalyst damage.
Again, there is no need to panic, but seek
attention as soon as possible. The blinking
light means that damage could result.
Are repairs more expensive?
Generally, repairs made in response to the
OBD system are no more expensive than
those made in response to traditional
tailpipe emissions-related repairs. If repairs
are made soon after the OBD “Check
Engine” light coming on, you may save your-self
more costly repairs that you might not
have identified without the OBD warning.
How is emissions testing done on
One of the benefits of the OBD system is
the ability to “ask the computer” how the
engine is performing. At an emissions
inspection station, the technician simply
connects the station computer to the vehicle
computer through a cable called a diagnostic
link connector. The vehicle computer then
directly communicates the specific operating
and emissions information needed for
Arrow points to OBD connector under dashboard.
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