vEPA
United States EPA420-F-03-042
Environmental Protection
Agency December 2003
On-Board Diagnostic (OBD)
Regulations and Requirements:
Questions and Answers
Certification and Compliance Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
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1. What is the origin of vehicle On-Board Diagnostic (OBD) systems?
In the early 1980s, vehicles were equipped with electronics and on-board computers to
control many of the engine control systems, such as fuel and ignition. As the engines
became more complex, it became necessary for vehicle manufacturers to develop a
more efficient method of monitoring for and diagnosing electronic component problems.
As a result, the vehicle manufacturers developed the first computerized, on-board
diagnostic systems.
2. What is OBD and how does it work?
On-Board Diagnostics is additional computer software that monitors the emission
control and emission-related components/systems, along with certain engine
components that provide vehicle operational information. By monitoring and evaluating
the various components and systems, the on-board computer is able to determine the
presence of a malfunction or deterioration that can affect emissions and illuminate the
"Check Engine" or "Service Engine Soon" light (also known as the malfunction indicator
lamp or MIL) on the dashboard. In some instances, the computer software may identify
a problem before there is an overt indication to the vehicle operator. The combination of
the various emission control and engine components/systems, the MIL, and the
diagnostic computer software make up the On-Board Diagnostic system.
3. What is the difference between the terms "OBD" and "OBD II"?
The terms "OBD" and "OBD M" are used interchangeably to describe the second-
generation of On-Board Diagnostics. The first generation of On-Board Diagnostic
requirements, called OBD I, was developed by the California Air Resources Board
(ARB) and implemented in 1988. As technology and the desire to expand On-Board
Diagnostic capability increased, a second-generation of On-Board Diagnostics
requirements was envisioned. Consequently, in 1992, ARB published their second
version of On-Board Diagnostic regulations called "OBD II", and in 1993, EPA published
their first version of On-Board Diagnostic regulations called "Federal OBD". Due to the
difference in revision level for ARB and EPA, the terms "OBD M" and "OBD",
respectively, emerged. However, as ARB and EPA regulations were further
harmonized, the terms began to be used interchangeably to represent the second-
generation of On-Board Diagnostics. (Refer to Attachment A of this document for a
complete timeline of OBD regulatory implementation).
4. What is the difference between OBD I systems and OBD II systems?
The general differences between OBD I and OBD II can be summarized as follows:
-i-
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OBDI
Monitors and detects component and system
electrical failures.
OBDII
Monitors and detects emission system
deterioration and/or malfunction as well as
electrical failures.
Malfunction indicator lamp (MIL) extinguishes
immediately if problem did not re-occur.
Malfunction indicator lamp (MIL) extinguishes
after 3 consecutive trips where the problem did
not re-occur.
Emission control or emission related components
that OBD must monitor, oxygen sensors, exhaust
gas re-circulation (EGR) system, fuel delivery
system, Powertrain Control Module (PCM) and
other electronic components at manufacturers
discretion.
Emission control or emission related components
that OBD must monitor, catalyst efficiency, oxygen
sensor response and heater, exhaust gas re-
circulation (EGR) system, fuel delivery system,
engine misfire, evaporative system, secondary air
system, air conditioning system using R-12,
Powertrain Control Module (PCM), and all
electronic inputs/outputs to the PCM.
Non-Standardized:
Connector location and design, diagnostic trouble
codes, terminology, definitions, communications
format, and acronyms are not standardized and
are implemented at the manufacturer's discretion.
Standardized:
Connector location and design, diagnostic trouble
codes, terminology, definitions, communications
format, and acronyms required for all
manufacturers.
5. What systems and components are required to be monitored in the Federal
OBD regulations?
The Clean Air Act Amendments (CAAA) of 1990 required, at a minimum, the monitoring
of the catalyst and the oxygen sensor. Federal OBD regulations extended the
monitoring requirements beyond just the catalyst and oxygen sensors and added
monitoring of other emission control and emission-related components such as:
exhaust gas re-circulation (EGR), secondary air, misfire, fuel metering/trim, oxygen
sensor heater, catalyst heater, air conditioning system (if R-12 refrigerant is used),
evaporative system, and any electronic emission related components. See the
applicable regulations for further detail (a list is provided in Attachment B of this
document).
6. What is a waiver, what is a deficiency, and how do they differ?
A waiver is an exemption from an entire monitoring requirement whereas a deficiency is
an exemption from a specific aspect of a monitoring requirement. Waivers (only for MY
1994 and 1995 vehicles) and deficiencies (MY 1996 and beyond) must be requested by
the manufacturer prior to certification. EPA can grant or deny the waiver or deficiency
based on specific regulatory criteria.
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For example, if a manufacturer was having difficulty implementing an oxygen sensor
monitor on a 1994 or 1995 model year vehicle, the manufacturer could request a waiver
and, if granted by the EPA based on the specific regulatory criteria, would be exempt
from implementing all of the oxygen sensor monitoring requirements. In contrast, for a
1996 model year and beyond vehicle, if a manufacturer is having difficulty implementing
an oxygen sensor monitor, the manufacturer is still required to perform some checks of
the oxygen sensor but may request a deficiency for specific checks that cannot be
performed. Therefore, the manufacturer still performs some level of oxygen sensor
monitoring but not the full level of monitoring that is expected and/or required.
Unlike ARB, which levies fines for more than two deficiencies (fixed amount assessed
per vehicle per deficiency), EPA does not levy fines for deficiencies. However, it is
EPA's intent to allow one deficiency per model year for each certified OBD system and
to limit the carry-over of deficiencies into subsequent model years.
7. Federal OBD regulations were required in 1994, but 1996 is commonly
referenced as the year of implementation. What are the reasons for this?
The OBD requirements were implemented beginning with the 1994 model year.
However, as discussed above, vehicle manufacturers were allowed to request waivers
from OBD monitoring requirements for the 1994 and 1995 model years. Since most
manufacturers requested and received OBD waivers during the 1994 and 1995 model
years, 1996 is commonly identified as the first year of full implementation once waivers
were no longer available.
8. What vehicles and weight classes does Federal OBD apply to and in what
model years were they implemented?
Federal OBD requirements apply as follows:
Category
Implementation Schedule
Light-Duty Vehicles and Trucks
(LDV/Ts) below 8,500 pounds
GVWR* w/ gasoline engines
-1994 Model Year
- Waivers available for 1994 and 1995 model years
-1996 model year: waivers not available, full compliance required
Light-Duty Vehicles and Trucks
(LDV/Ts) below 8,500 pounds
GVWR w/ diesel engines (see
#7 below for further discussion)
- 1994 Model Year
- Waivers available for 1994-1996 model years
-1997 model year: waivers not available, full compliance required
- 2005: aftertreatment monitoring (i.e, monitoring of catalyst,
adsorbers, particulate filters, etc.) is required
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Heavy-Duty engines and
complete vehicles between
8500-14,000 pounds GVWR **
Alternate Fuel Vehicles
Heavy-Duty engines and
complete vehicles above 14,000
pounds GVWR
Phase-In Based on Projected Sales
Model
Year
2004
2005
2006
2007
2008
Gasoline Engines/Vehicles
40%
60%
80%
80%
Diesel Engines/Vehicles
~
50%
50%
100%
100% (full compliance)
(see #1 2 below for further discussion)
At this time, there are no requirements for engines/vehicles above
14,000 pounds GVWR.
* GVWR = Gross Vehicle Weight Rating.
**ARB has had requirements for all vehicles below 14,000 pounds GVWR since the 1996 model year,
except diesel vehicles which were not required to have OBD until the 1997 model year.
9. What components/systems on diesel engines/vehicles are monitored by
OBD?
The main diesel components monitored for OBD include, but are not limited to, exhaust
gas re-circulation (EGR), misfire (complete lack of cylinder combustion), glow plugs and
any electronic inputs and outputs to the powertrain control module (PCM).
Due to differences in operation and pollutant criteria, diesel engines do not have the
same components and the same OBD monitors as gasoline engines. The main
pollutant from diesel engines tends to be oxides of nitrogen (NOx) and particulate
matter (PM) versus gasoline engines which, in addition to NOx and PM, produce
hydrocarbon (HC) and carbon monoxide (CO) emissions. Specifically, diesel engines
do not typically use a three-way catalyst (TWC), oxygen sensors, and evaporative
monitors as compared to their gasoline counterparts.
As the NOx and PM emission standards are lowered for diesels, aftertreatment devices
(i.e., NOx adsorbers, particulate filters, etc.) may be necessary to meet the emission
standards. As a result, diesel engines/vehicles will be required to monitor aftertreatment
devices, if equipped, as described in Attachment C.
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10. What are the major differences between Federal OBD and California Air
Resources Board (ARB) OBD II? How has this changed over the years?
ARB OBD II requirements tend to focus on OBD system design and, as a result, are
more technology forcing and provide greater detail for each required OBD monitor. In
contrast, Federal OBD regulations tend to focus on the emission performance aspects
of emission control and emission-related powertrain systems/components and are more
general in description than ARB OBD II regulations. Although the philosophies are
different, both are equally comprehensive and effective at ensuring proper design of
OBD systems.
The key difference between Federal and ARB OBD regulations are primarily in the area
of evaporative system leak diagnostics. Federal OBD requires detection of a 0.040" or
greater orifice (i.e., leak, crack, gap, hole) in the evaporative system. In contrast, ARB
OBD II requires detection of a 0.020" or greater orifice (i.e., leak, crack, gap, hole) in
the evaporative system. There are instances where manufacturers may choose to
retain 0.020" leak detection capability on Federal vehicles (i.e., vehicles for sale outside
of California), but they are not required to at this time by Federal OBD regulations.
Since EPA accepts compliance with ARB OBD II design requirements, most
manufacturers prefer to certify to ARB OBD II design requirements. Over the years,
EPA has revised the Federal OBD regulations to harmonize with ARB OBD II
regulations to reduce manufacturer certification burden (i.e., one system for all 50
states). The Vehicle Emissions Certification Information (VECI) label under the vehicle's
front hood should indicate which regulations the vehicle complies with.
11. Are there other countries that have OBD requirements? If so, what are they
and what are the major differences between U.S. OBD systems and these
other countries' OBD systems?
Canada: Canada's OBD requirements are essentially similar to EPA's requirements.
Likewise, Canada also accepts ARB OBD II systems as EPA does.
European Union (EU): The EU's requirements closely mirror EPA's requirements.
However, the EU does not require the OBD system to monitor for the presence of
evaporative system vapor leaks and, as a result, the manufacturer or importer must
modify a European OBD system to include evaporative system vapor leak diagnostic
capability before receiving EPA Federal OBD approval. The European OBD regulations
can be found in the Directive 98/69/EC, which contains rules for light-duty vehicles.
Japan: Japan has developed a simple form of OBD requirements. Japan focuses on
light duty OBD systems as well, though it is not described in the same detail as in the
U.S. regulations. According to Japanese certification standards, California, U.S. and
European OBD systems are considered equivalent.
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Other countries are also considering adopting OBD requirements along with more
stringent emission standards, but have not done so yet.
12. What are the OBD requirements for Alternative Fuel Vehicles?
Dedicated alternate fuel, dual-fuel, bi-fuel, or flexible fuel vehicles are not required to be
fully compliant with Federal OBD II requirements during alternate fuel operation until the
2005 model year. Hybrid, electric, and fuel cell vehicles are also considered "alternate
fuel" vehicles and are therefore required to meet similar Federal OBD requirements as
alternate fuel vehicles.
For dual fuel, bi-fuel or flexible fuel vehicles beginning with the 1996 model year, the
OBD system was required to be fully functional during gasoline operation. However,
some manufacturers required additional lead time and were granted waivers during
gasoline operation until the 1999 model year. OEMs or vehicle converters of dual fuel,
bi-fuel or flexible fuel vehicles must also ensure that the integrity of the OBD data
stream information is maintained regardless of the fuel the vehicle is operated on (i.e.,
information pertaining to a trouble code, MIL status, and other OBD data stream fault
recorded during gasoline operation should be retained even if the vehicle is switched to
alternate fuel operation).
In summary, all alternate fuel vehicles will have OBD II in the 2005 model year
regardless of the operating fuel-type. All dual fuel, bi-fuel or flexible fuel vehicles
between the 1999 and 2004 model year and most dual fuel, bi-fuel or flexible fuel
vehicles between 1996 and 1999 will have full OBD II capability on the gasoline side.
13. What are the OBD requirements for Hybrid Electric and Fuel Cell Vehicles?
The requirements for Hybrid Electric Vehicles (HEVs) are as follows:
The manufacturer must equip each HEV with:
*• a maintenance indicator that illuminates when the minimum performance
level for each battery system is observed;
> a separate odometer or other device that can accurately measure the
mileage accumulation on the engines used on these vehicles;
*• and, for HEVs with off-board charging capability, a useful life indicator that
must illuminate when the battery system is unable to achieve an all-
electric operating range (i.e., at least 75 percent of the full range for the
vehicle determined on the Urban Driving Schedule (UDS) portion of the
All-Electric Range Test).
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At this time, there are no OBD requirements for Fuel Cell vehicles since they are zero
emitting. There may be maintenance and safety indicators used but this is not a result
of OBD requirements.
14. What are the latest related Code of Federal Regulations (CFR) cites, EPA
web sites, and Federal Register cites related to OBD?
CFR Cites:
OBD (engine certification) - 40 CFR part 86, section 86.005-17
OBD (chassis certification) - 40 CFR part 86, section 86.1806-05
Certification information requirements - 40 CFR part 9, section 9.1844-01
OBD checks in Inspection and Maintenance Programs - 40 CFR part 51 and 85
Web sites:
Code of Federal Regulations - http://www.access.gpo.gov/nara/cfr/cfr-table-search.html
General OBD info and regulations - http://www.epa.gov/otaq/obd.htm
*You can retrieve CFR sections by using the CFR citations listed in Attachment B (e.g.,
40 CFR 86.094-17)
ARB OBD - http://www.arb.ca.gov/msDrog/obdDrog/obdprog.htm
15. Who should I contact if I have additional questions regarding OBD?
Since there are many aspects of OBD, there are individuals assigned to specific areas
of OBD but you can contact any of the following individuals for OBD questions:
OBD Regulations and Policy, Light-Duty/Heavy-Duty OBD Certification and
Compliance'.
Arvon L. Mitcham
(734)214-4522
mitcham.arvon@epa.gov
OBD Inspection and Maintenance Implementation - Technical Issues'.
Jim Lindner
(734)214-4558
lindner.jim@epa.gov
OBD Outreach and Service Information (i.e., OBD emissions-related service materials)
Holly Pugliese
(734)214-4288
Dugliese.hollv@eDa.gov
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Attachment A
History of On-Board Diagnostics (OBD)
Late 1970s Auto manufacturers developed diagnostic systems to check engine
- 1980s performance through the use of electronic feedback control
Mid-1980s U.S. Environmental Protection Agency (EPA) and California Air
Resources Board (ARB) researched OBD system for emissions purposes
1988 ARB published regulations on OBD I (simple, high-level check)
1990 Clean Air Act amended; EPA directed to promulgate OBD regulations
building on ARB OBD I regulations
1991 EPA published Notice of Proposed Rulemaking for Federal OBD systems
1992 ARB published regulations on second generation of OBD regulations,
commonly called OBD II (more comprehensive monitoring/ checks
included)
1993 EPA published Final Rule for Federal OBD systems; differs from ARB
OBD II in terms of emission exceedance criteria (additive for EPA vs.
multiplicative for ARB); the number of required monitors and evaporative
system leak criteria (diurnal emission based for EPA vs. orifice size-based
for ARB)
1994/95 EPA implementation begins for light-duty vehicles/trucks less than 8,500
pounds GVWR (ARB OBD II required for all vehicles less than 14,000
pounds GVWR); waivers are allowed for monitored systems, an option
almost all manufacturers choose
1996 Full OBD II system compliance is required; waiver option is eliminated
although deficiencies for minor OBD system short falls are allowed
1998 EPA published rule that harmonizes Federal OBD requirements with ARB
OBD II; adopts multiplicative threshold approach and 0.040" leak
monitoring requirement
1999 EPA added provision that requires Federal OBD on complete vehicles
between 8,500 pounds and 14,000 pounds GVWR to accompany the
requirements for light-duty vehicle/trucks below 8,500 pounds
2000/01 EPA adds separate OBD requirements for gasoline and diesel engines,
and new aftertreatment monitoring requirements for all diesel
engines/vehicles intended for use in vehicles less than 14,000 pounds
GVWR
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Attachment B
Federal Register Cites: On-Board Diagnostics (OBD) Regulatory Actions
June 8, 2001 Service Information NPRM
66 FR 30830 [40 CFR B86.094-38, B86.096-38 and B86.1808-01 -38]
January 18, 2001 OBD for HD Vehicles and Engines - Modification of Federal
66 FR 5041 OBD requirements; part of the 2007 HD FRM
[40 CFR B86.005-17 and B86.1806-05]
October 6, 2000 OBD for HD Vehicles and Engines - part of the 2004 HD FRM
65 FR 59916 [40 CFR B86.005-17 and B86.1806-05]
October 29, 1999 OBD for HD Vehicles and Engines - part of the 2004 HD
64 FR 58472 NPRM [40 CFR B86.1806-01]
December 22, OBD FRM: Modification of Federal OBD for LDVs and LDTs;
1998 Extension of Acceptance of California OBD II Requirements
63 FR 70681 (Harmonization FRM) [40 CFR B86.099-17]
April 27, 1998 OBD FRM: OBD Check in I/M: Final rule to delay incorporation
63 FR 24429 of OBD checks in I/M programs until 1/1/2001
[40 CFR parts 51 and 85]
February 19, 1998 OBD Proposed Rule Notice of Document Availability: ARB
63 FR 8386 MO#97-24 containing OBD II regs. proposed for federal
certification option via the Harmonization NPRM (5/28/97)
[40CFRB86.099-17]
February 17, 1998 OBD FRM: Modification of Federal OBD for LDVs and LDTs;
63 FR 7718 Extension of Deficiency Policy for 99MY [40 CFR B86.094-17]
December 22, OBD NPRM: OBD Checks in I/M; Proposal to delay
1997 incorporation of OBD checks in I/M programs until 1/1/2001
62 FR 66841 [40 CFR parts 51 and 85]
May 28, 1997 OBD NPRM: Modification of Federal OBD for LDVs and LDTs;
62 FR 28932 Extension of Acceptance of California OBD II Requirements
(Harmonization NPRM) [40 CFR B86.094-17]
October 11,1996 OBD II Waiver Decision: California State Motor Vehicle
61 FR 53371 Pollution Control Standards; Waiver of Federal Preemption;
Decision
August 30, 1996 OBD FRM: Acceptance of Revised California OBD II
61 FR 45898 Requirements contained in MO#95-34 [40 CFR B86.094-17]
August 6, 1996 OBD FRM: OBD Checks in I/M
61 FR 40940 [40 CFR parts 51 and 85]
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November 1, 1995 OBD NPRM: Acceptance of Revised California OBD II
60 FR 55521 Requirements [40 CFR B86.094-17]
August 18, 1995 OBD NPRM: OBD Checks in I/M
60 FR 43092 [40 CFR parts 51 and 85]
August 11,1995 OBD Notice of opportunity for public hearing and public
60 FR 41066 comment period: California State Motor Vehicles Pollution
Control Standards; Opportunity for Public Hearing
August 9, 1995 OBD FRM: Regulations Requiring Availability of Information for
60 FR 40474 Use of On-Board Diagnostic Systems and Emission-Related
Repairs on 1994 and later Model Year Light-Duty Vehicles and
Light-Duty Trucks [40 CFR B86.094- 38]
August 2, 1995 OBD DFRM: Revision to Requirements for Storage of Engine
60 FR 39264 Conditions Associated With Extinguishing a Malfunction
Indicator Light [40 CFR B86.094-17]
July 25, 1995 OBD Removal Notice: Regulations Allowing Optional
60 FR 37945 Compliance with California OBD II Requirements as Satisfying
Federal OBD
March 23, 1995 OBD DFRM: Acceptance of Revised California OBD II
60 FR 15242 Requirements; OBD Relief for Alternative Fueled Vehicles; and
Revisions for Consistency Between Federal OBD and
California OBD II; Removal of Federal Anti-Tampering
Provisions [40 CFR B86.094-17]
October 7, 1994 OBD Notice of Court Decision Regarding Agency Regulations:
59 FR 51114 Regulations Requiring Tampering Prevention for On-Board
Diagnostic Systems
July 28, 1994 OBD Technical Amendment: OMB Approval Numbers Under
59 FR 38372 the Paperwork Reduction Act
February 19, 1993 OBD FRM
58 FR 9468 [40 CFR B86.094-17]
December 13, OBD Extension of comment period
1991
56 FR 65035
September 24, OBD NPRM
1991 [40CFRB86.094-17]
56 FR 48272
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Attachment C
Overview of On-Board Diagnostic (OBD) Monitoring Requirements for EPA, ARB and Europe
Monitoring Requirement
Catalyst
Catalyst Heater
Misfire Detection
Evaporative System
Secondary Air
Air Conditioning
Fuel System
Oxygen Sensor
Oxygen Sensor Heater
Exhaust Gas Re-circulation (EGR)
Positive Crankcase Ventilation (PCV)
Thermostat Monitoring
Fuel Filler Cap
Particulate Filter
Comprehensive Component Monitoring
U.S. EPA Federal OBD
Otto-
o
0
o
o
0
g
o
o
0
0
b
b
f
X
o
Diesel
a,b
a,b
d
X
X
g
X
a
a
0
b
b
X
b,c
O
ARB OBD II
Otto-
o
0
o
o
0
0
o
o
0
0
o
o
0
X
o
Diesel
a,b
a,b
d
X
X
0
O
O
0
0
O
O
X
b,c
O
European OBD
Otto-
o
e
O
X
e
X
e
O
0
e
e
e
0
X
O
Diesel
o
e
e
X
e
X
O
X
X
e
e
e
0
0
O
O = required, X = not required; refer to the letters below for clarification on some requirements (also refer to the applicable regulations for additional
details)
a: If the vehicle is equipped with this component/system, it must be monitored
b: Must be monitored unless failure would not cause an emissions exceedance (must be demonstrated/supported with test data)
c: Must be monitored for catastrophic failure only
d: Must monitor for complete lack of cylinder combustion only
e: Covered by a general statement under comprehensive component monitoring
f: Failure should be detected by evaporative system; for a missing cap, a separate fuel cap indicator light may be used
g: Required to be monitored if R-12 is used
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