What is OBD II?
OBD II is an acronym for On-Board Diagnostics II, the second generation
of on-board self-diagnostic equipment requirements for
California vehicles. On-board diagnostic capabilities are incorporated
into the hardware and software of a vehicle's on-board computer to
monitor virtually every component that can affect emission performance.
Each component is checked by a diagnostic routine to verify that it is
functioning properly. If a problem or malfunction is detected, the OBD
II system illuminates a warning light on the vehicle instrument panel
to alert the driver. This warning light will typically display the
phrase "Check Engine" or "Service Engine Soon." The system will also
store important information about the detected malfunction so
that a repair technician can accurately find and fix
What was OBD I?
On-Board Diagnostics I (OBD I) was California's first OBD regulation
which required manufacturers to monitor some of the emission control
components on vehicles. Required on all 1991 and newer vehicles, OBD I
systems were not as effective as possible because they were limited to
monitoring only a few of the emission-related components and they were
not calibrated to a specific level of emission performance. OBD II was
developed to address these shortcomings and make the system
more user-friendly for service technicians.
Why is OBD II
Even though new vehicles sold in California are the cleanest in the
world, the millions of cars on the road and the ever increasing miles
they travel each day make them our single greatest source of smog
forming emissions. While the new vehicles in California may start out
with very low emissions, improper maintenance or faulty components can
cause the vehicle emission levels to sharply increase. Studies
estimate that approximately 50% of the total emissions from late-model
vehicles are the result of emission-related malfunctions. OBD II works
to ensure that the vehicles remain as clean as possible over
their entire life.
Does my car have
All 1996 and newer gasoline and alternate fuel passenger cars and
trucks are required to have OBD II systems. All 1997 and newer
diesel fueled passenger cars and trucks are also required to meet the
OBD requirements. Additionally, a small number of 1994 and
1995 model year gasoline vehicles were equipped with OBD II
systems. To verify that your vehicle is equipped with OBD II,
you can look for the words "OBD II" on the emission control information
label attached to the underside of the vehicle hood.
Do other states
require OBD II?
Yes. The United States Environmental Protection Agency (EPA) requires
all 1996 and newer vehicles sold in any state to meet the EPA
OBD requirements. While EPA's OBD requirements currently are slightly
different from California's OBD II requirements, systems
designed to meet California's requirements are also accepted
by EPA as meeting the federal requirements. In practice,
virtually all vehicles sold in the U.S. are designed and certified to
meet California's OBD II requirements, regardless of where in the U.S.
they are sold.
What should I do if
the warning light comes on?
Most manufacturers advise having the vehicle serviced as soon as
conveniently possible. Since there are many different problems that can
cause the light to illuminate, it is hard to generalize how severe a
problem may be. However, often the problem will have a
noticeable effect on fuel economy, performance,
or driveability of your vehicle, and extended driving without
fixing the problem could possibly even damage other components.
Additionally, there are certain malfunctions that can cause the warning
light to blink. This indicates that a malfunction is currently
occurring which could be damaging your catalytic converter. Because
replacement of the catalyst can be expensive, many manufacturers
recommend having the vehicle serviced as soon as possible if the
warning light is blinking.
Does the warning
light only mean the emissions controls on my car aren't working?
While all malfunctions that cause the light to illuminate do affect
emissions, many also can affect fuel economy and several can
cause driveability problems or a decrease in overall
performance. Manufacturers generally optimize their vehicles for
performance, fuel economy, and emissions. As such, virtually any
malfunctioning component can result in the vehicle running in a
condition that is less than optimal.
Do I have to go to
the dealer to get my OBD II car fixed?
No. Properly trained and equipped independent shops are capable of
utilizing the diagnostic information from the OBD II system
and can make repairs just like dealers. In fact,
several of the provisions incorporated in the OBD II regulation are
intended to make it easier for independent shops to diagnose
and repair vehicles accurately and in a cost-effective manner.
It should be noted, however, that California's emission
warranty requires the vehicle manufacturer to repair under warranty any
problem that the OBD II system detects if the vehicle is less
than three years old and has less than 50,000 miles and only
dealers are allowed to perform warranty work. Further,
major emission components which exceed a defined cost limit
at the time the vehicle was produced (currently about $500) are
covered for 7 years or 70,000
miles - this list of covered parts, which varies from car to
car, should be listed in the owner's manual or accompanying
that came with the vehicle. Additionally, if you have
a vehicle that is certified by ARB as a partial zero emission vehicle
(PZEV), any problem detected by the OBD II system is covered under
warranty as long as the vehicle is less than 15 years old and has less
than 150,000 miles. A list of vehicles that are certified as PZEVs
can be found at ARB's Drive
Clean website (select vehicles with a Smog Score of 9 to show PZEVs).
How is Smog Check
affected by OBD II?
In all areas of the state, technicians
are required to perform an OBD II check (visual and
functional) during the Smog Check inspection. Specifically,
the technician visually checks for a functioning and an illuminated
warning light and the Smog
Check test equipment communicates with the on-board computer for fault
information. If a fault is currently causing
the light to
be on, you need to have the malfunctioning component
repaired before you can pass the test.
Additionally, if too
many readiness flags are "incomplete," the vehicle will fail
inspection because it has not
been operated enough to allow all
of the self-diagnostics to run. This can occur if a
has recently been repaired, if you have recently had
or disconnected battery, or if your vehicle battery
been replaced. It does not necessarily mean that anything is
wrong with your car - it simply means that the vehicle hasn't had a
chance to run all of its self-diagnostics to confirm that everything is
okay. The vehicle will need
to be driven more before the vehicle can be tested
to pass. Vehicle owners who fail Smog Check due to
incomplete readiness flags should drive their vehicle as they normally
do for about a week or so to set these readiness flags to "complete."
If the incomplete readiness flags were most likely not a
result of a recently disconnected/replaced vehicle battery, or if the
vehicle owner does not normally drive the vehicle that often, then the
vehicle owner should seek technician help in setting the flags.
The technician should either advise the owner of specific
driving patterns needed to set the flags or operate the vehicle himself
(most likely on a dynamometer in the shop) and check with his scan tool
to determine which monitors have completed. In the future,
OBD II-equipped vehicles
may not even have to undergo a tailpipe
test. Technicians would simply be required to perform the OBD
inspection. More detailed information about California's current OBD
II-based Smog Check program can be found at BAR's Smog
Does OBD II prevent
me from modifying (or using non-OEM parts on) my car?
No. As in the past, aftermarket parts manufacturers continue
produce parts to fit most vehicles. Despite OBD II,
the vast majority
of parts on a new vehicle
are functionally identical or very similar to
pre-OBD II equipped vehicles. For add-on or
performance enhancing parts, aftermarket manufacturers are
still required to obtain an exemption
from the Air Resources Board before being
legal for sale in California. Already, performance
parts have been approved for many OBD II equipped vehicles and
they should be available in the future as well. Parts that
been granted such approval can be found at ARB's aftermarket
If I need to
replace the catalyst (or catalytic converter) on my OBD II car, can I
use any catalyst that is available?
California has specific regulations defining minimum
performance levels for catalysts on all cars including OBD II-equipped
cars. Replacement catalysts available from the dealer for
your specific vehicle are legal. Additionally, aftermarket
catalysts which have been approved by ARB are legal for use on cars in
California. If you are purchasing a new catalyst for your OBD
II vehicle, you need to make sure it is approved by ARB for use on your
specific vehicle. Approved aftermarket catalytic converters
can be found by going to ARB's aftermarket
selecting "OBD II catalytic converter" as the device type under the
"List Executive Orders by Device" section.
The aftermarket catalyst manufacturers also have catalogs and
sometimes websites that identify which catalysts are approved for
specific vehicles in California.
How much do OBD II
systems add to the cost of a new car?
In most cases, equipping a new vehicle with an OBD II system has only
required minimal additional hardware, resulting in only slight
additional costs. This is because most OBD II requirements are
usually met by new software in the vehicle's on-board
computer. In 1996, the federal government estimated that the OBD II
requirements increased the retail cost of a 1996 model year new vehicle
by an average of $61. Overall, OBD II is anticipated to
in cost-savings to the consumer by catching faults quickly
(before other components can be damaged) and by pinpointing the source
of the fault to aid technicians in making fast,
What is OBD III?
First, there is no such thing. There has been speculation
about a new OBD program that would utilize remote transponders (like
those currently used for automated bridges or toll roads) to send
information indicating if any malfunctioning component is present in
the vehicle in lieu of having the vehicle inspected at a Smog Check
facility every one or two years. Many have referred to such a
concept as OBD III. However, contrary to the rumors, no such
program has been adopted by ARB nor have any decisions been made by ARB
to pursue such an approach in California. The concept
exists and there are various products consumers can buy to remotely
monitor their vehicle. Some other states are even pursuing
programs and allowing consumers who voluntarily equip their vehicles
with such devices to be exempted from their inspection programs that
are similar to California's Smog Check. These other states
pursued such approaches as additional ways to reduce consumer
inconvenience and costs of participating in the inspection program.