United States             Air and Radiation         EPA420-F-98-017
                  Environmental Protection                          April 1998

                  Office of Mobile Sources
&EPA       Regulatory
                  Final Rule Amendment to On-Board
                  Diagnostic Checks Requirement for
                  I/M Programs
                  The U.S. Environmental Protection Agency (EPA) is extending, by a
                  period of three years, the deadline by which states must implement On-
                  Board Diagnostic (OBD) checks as a regular part of their Inspection and
                  Maintenance (I/M) programs. Prior to this new deadline of January 1,
                  2001, states may opt to include OBD checks and fail vehicles based on
                  OBD failure alone. States may not earn emission reduction credit,
                  however, unless exhaust and evaporative tests are performed as well.
                  Should EPA and states complete testing and review of OBD systems
                  sooner than expected, the Agency may be able to make credits
                  available to states who choose to implement OBD I/M checks prior to
                  the new deadline.

                  On August 6, 1996, EPA published a final rulemaking relating to the
                  implementation of OBD checks as a routine part of I/M programs. In the
                  rule, EPA interpreted the Clean Air Act requirement to include both
                  emission testing and OBD checks and thus required both tests as part of
                  the regular I/M test procedures. Ozone Transport Region (OTR) areas
                  with OTR low enhanced programs were to implement OBD checks by
                  January 1, 1999, and all other areas were to implement OBD checks by
                  January 1, 1998. Until January 1, 2000, OBD checks, exhaust tests and
                  evaporative system tests, where applicable, were to be required on each
                  subject vehicle of model year 1996 and newer. After January 1, 2000,
                                                         > Printed on Recycled Paper

failure of the OBD test would require mandatory repair. On December
22, 1997, EPA published a Notice of Proposed Rulemaking (NPRM) (62
FR 66841) which proposed delaying the implementation of mandatory
OBD checks until January 1, 2001.
Overview of Final Rule

This rule delays the required implementation date for OBD by setting the
new implementation deadline as January 1, 2001, for all areas with basic
and enhanced I/M programs. This amounts to a two year delay for OTR
low enhanced areas and a three year delay for all others. During this time
extension, EPA will work with states and other stakeholders to generate,
collect and analyze the data necessary to determine the effectiveness of
OBD systems in an I/M setting.

EPA is currently conducting such a study which began October 1, 1997.
Two years are needed to ensure ample time for fleet penetration of OBD-
equipped vehicles, so that enough vehicles can be recruited for the study.
A third year will be needed to allow sufficient time to analyze the data
generated by the study.

In addition, EPA has made certain clarifying amendments to allow for
updates to the Code of Federal Regulations which are cross-referenced in
the OBD rule. Section 86.094-17,  which includes the technical specifica-
tions for OBD systems, is periodically updated to include new require-
ments. This rule amends the sections of the OBD rule where that subsec-
tion is referenced with new language which obviates the need for future
amendments in this regard.

This rule does not affect the requirement that states revise their I/M State
Implementation Plans by August 6, 1998, to include the OBD checks.
Also unchanged are the sections which allow states the option to imple-
ment OBD inspections before December 31, 1999, and to allow failure
of OBD to result in failure of the I/M test, thereby requiring repair.
However, states which choose to conduct OBD checks cannot earn
emission reduction credits for doing so unless they also perform the
exhaust and evaporative tests, where applicable, or unless EPA completes
its analysis and determines appropriate credit sooner than expected.

Effect of Final Rule

This rule will allow the states even greater flexibility in designing and
implementing I/M programs which meet their local needs and help them
to move towards attainment. In addition, it will reduce the cost burden
the states would face if they were required to run OBD checks concur-
rently with the exhaust and evaporative tests as required by the previous
rule, so this amendment will produce a net savings. The I/M testing
requirements will now be less burdensome in terms of test time, equip-
ment and cost. Furthermore, it is not certain that the requirement would
have generated additional emission reductions to justify the added cost.

OBD equipment suppliers and I/M contractors may need to adjust to
shifting requirements resulting from this rule. Automobile manufacturers
may see a delay in the generation of some data on OBD in-use perfor-
mance. The general public will not be affected by the delay, as it only
postpones a requirement to which most have not yet been subjected.

The delay will have no appreciable effect upon the environment.  The
vehicles which would otherwise be subject to the OBD check will still
receive exhaust and evaporative (where applicable) testing, if the state is
earning emission reduction credits for those vehicles. Emission reduc-
tions will still be achieved for those vehicles despite the delay in OBD
For More Information

Additional documents on I/M programs and OBD are available electroni-
cally from the EPA Internet server at:

       http ://www. epa.gov/OMSWWW/im.htm

Document information is also available by writing to:

       U.S. Environmental Protection Agency
       Office of Mobile Sources
       2565 Plymouth Road
       Ann Arbor, Michigan 48105