1State  of California  
Air Resources  Board
Notice  of Public  Availability  of Modified  
Text
Proposed  Amendments  to the Heavy -Duty  Engine  and 
Vehicle  Omnibus  Regulation
Public  Hearing  Date:  October  20, 2023
Public  Availability  Date:  December  6, 2023
Deadline  for Public  Comment:  December  21, 2023
By notice  posted  on the California  Air Resources  Board ’s (CARB  or Board)  webpage  on 
August  1, 2023,  and published  in the August  4, 2023,  California  Regulatory  Notice  Register  
(Register  2023,  Number  31-Z), CARB  announced  a public  comment  period  for the Proposed  
Amendments  to the Heavy -Duty Engine  and Vehicle  Omnibus  Regulation.  CARB  subsequently  
received  several  requests  for a public  hearing,  and CARB ’s Executive  Officer  (EO)  conduct ed 
a hearing  on October  20, 2023 , to consider  approving  the proposed  amendments , under  the 
authority  delegated  to the EO pursuant  to Resolution  23-15.
CARB  staff has determined  that additional  modifications  to the initially  proposed  amendments  
are appropriate  and has developed  the proposed  modifications  (15-Day Changes)  as stated  
below  in the “Summary  of Proposed  Modifications”  section  of this notice.  The Append ices 
showing  the specific  proposed  modifications  to the text of the proposed  regulation  being  made  
with these  15-Day Changes  are shown  in multiple  ways  in order  to meet  the requirements  of 
the Administrative  Procedure  Act (APA)  while  also posting  alternate/complementary  versions  
that provide  increased  accessibility  to view the modifications  in multiple  ways.
The proposed  modified  regulatory  language  is available  for public  comment  for a period  of at 
least  15 days  as required  by Government  Code  section  11346.8.  To be considered  by the EO, 
written  comments  must  be submitted  by December  21, 2023.
The text of the modified  regulatory  language  is shown  in Appen dices  A, B, and C.
The Appendices  are as follows:
Appendix  A – Amendments  to Sections  1956.8,  1971.1,  and 1971.5,  Title 13, California  Code  
of Regulations
Appendix  B – Amendments  to the Proposed  Modifications  to the Diesel  Engine  Test 
Procedures
Appendix  C - Amendments  to the Proposed  Modifications  to the Otto-Cycle  Engine  Test 
Procedures2The versions  of the appendices  available  for review  are provided  in multiple  ways,  as follows:
·Appendices  A-1 and B-1: Proposed  15-Day Modifications  to Proposed  
Regulation  Order  and Diesel  Engine  Test Procedures,  respectively,  (compared  to 
version  released  for 45-day comments)
·Appendices  A-2 and B-2: ~Alternative  format s to Appendices  A-1 and B-1, 
respectively ~
·Appendices  A-3 and B-3: Proposed  15-Day Modifications  to Proposed  
Regulation  Order  and Diesel  Engine  Test Procedures,  respectively,  
(15-Day Modifications  and 45-Day Modifications  combined  and compared  to 
existing  regulatory  text) in Alternative  format
·Appendix  C-1: Proposed  15-Day Modifications  to the Otto-Cycle  Engine  Test 
Procedures
·Appendix  C-2: ~Alternative  format  to Appendix  C-1.
The Appendices  showing  the specific  proposed  modifications  to the text of the proposed  
regulation  order  and Test Procedures  available  for comment  with this Notice  are provided  in 
the two formats  denoted  with the suffixes  “-1” and “-2.”
In the version s denoted  Appendix  A-1 and B-1, the 45-Day Changes  (proposed  regulatory  
language  as posted  on August  1, 2023)  are shown  in “normal  type.”  The deletions  and 
additions  to the 45-Day Changes  that comprise  the 15-day Changes  that are being  made  
public  and available  for comment  with this Notice  are shown  in strikeout  to indicate  deletions  
and underline  to indication  additions.
In the version s denoted  Appendix  A-2 and B-2, the 15-Day Changes  are provided  in a tracked -
changes  format  to meet  the requirement  for accessible  electronic  documents.  The 45-Day 
Changes  are incorporated  into this version  as plain,  clean  text because  they are not being  
made  available  for public  comment  by this Notice.  The Proposed  15-day Changes  are shown  
in tracked  changes  and are made  public  with this Notice  and available  for comment.  To review  
this document  in a clean  format,  without  underline  or strikeout  to show  changes,  that shows  all 
the proposed  regulations  being  considered  for adoption,  please  select  “Simple  Markup”  or “No 
Markup,”  or accept  all changes  in Microsoft  Word’s  Review  menu.  You can also change  the 
view to the initially  proposed  45-Day Changes  (originally  proposed  regulatory  text prior to 
these  proposed  modifications)  by selecting  “Original”  or rejecting  all tracked  changes.  
Additionally,  “Advanced  Track  Changes  Options”  will allow  for further  options  regarding  color  
and other  markings.
In the version s denoted  Appendix  A-3 and B-3, the existing,  original  regulatory  language  
currently  adopted  into the California  Code  of Regulations  (pre-45-Day Changes)  is shown  as 
plain,  clean  text, while  the 45-Day Changes  and the proposed  15-Day Changes  are combined  
and shown  in tracked  changes.  To review  the net proposal  in this document  in a clean  format  
(no underline  or strikeout  to show  changes),  please  select  “Simple  Markup”  or “No Markup”  in 
Microsoft  Word’s  Review  menu  or accept  all changes.  You can also change  the view to the 
original  (originally  proposed  regulatory  text prior to any proposed  modifications,  or 45-Day 
Changes)  by selecting  “Original”  or rejecting  all tracked  changes.  By progressing  through  the 
changes  and comparing  them  with the 15-Day Changes,  the public  can see the net and 
stepwise  changes  being  proposed  in relation  to existing  law. Please  refer to the version  
denoted  A-1 and B-1 to review  the 15-Day Changes  available  for comment  and its3companion/alternate  version  A-2 and B-2 to view an accessible  version  showing  the 15-Day 
Changes.
In the version  denoted  Appendix  C-1, The deletions  and additions  to the current  test procedure  
text that comprise  the Proposed  15-day Changes  which  are being  made  public  and available  
for comment  with this Notice  are shown  in strikeout  to indicate  deletions  and underline  to 
indication  additions.
In the version  denoted  Appendix  C-2, the Proposed  15-day Changes  are shown  in tracked  
changes  and are made  public  with this Notice  and available  for comment.  To review  this 
document  in a clean  format,  without  underline  or strikeout  to show  changes,  that shows  all the 
proposed  regulations  being  considered  for adoption,  please  select  “Simple  Markup”  or “No 
Markup,”  or accept  all changes  in Microsoft  Word’s  Review  menu.  You can also change  the 
view to original  test procedure  text by selecting  “Original”  or rejecting  all tracked  changes.  
Additionally,  “Advanced  Track  Changes  Options”  will allow  for further  options  regarding  color  
and other  markings.
In the Final  Statement  of Reasons,  staff will respond  to all comments  received  on the record  
during  the comment  periods.  The Administrative  Procedure  Act requires  that staff respond  to 
comments  received  regarding  all noticed  changes.  Therefore,  staff will only address  comments  
received  during  this 15-day comment  period  that are responsive  to this notice  or the changes  
detailed  in Appendi ces A, B, and C.
All regulatory  documents  for this rulemaking  are available  online  at the following CARB  
website :https://ww2.arb.ca.gov/rulemaking/2023/hdomnibus2023 .
Summary of Proposed Modifications
The following  summary  does  not include  all modifications  to correct  typographical  or 
grammatical  errors,  changes  in numbering  or formatting,  nor does  it include  all nonsubstantive  
revisions  made  to improve  clarity.
I. Title 13, California  Code  of Regulations,  section  1956.8  (13 CCR  1956.8)  Exhaust  
Emissions  Standards  and Test Procedures  - 1985  and Subsequent  Model  Heavy -Duty  
Engines  and Vehicles,  2021  and Subsequent  Zero -Emission  Powertrains,  and 2022  and 
Subsequent  Model  Heavy -Duty  Hybrid  Powertrains
1.In subsection  1956.8(a)(2)(C) 3.b.iv.1 , the text was modified  to further  clarify  the intent  of 
the regulations  for manufacturers  that use Option  1. The new language  states  that the 
excess  oxides  of nitrogen  (NOx) and particulate  matter  (PM) emissions  from this 
percentage  of heavy -duty legacy  engines  exceeding  the allowable  legacy  engine  sales  
limits  must  be offset  at 4 times  the deficit  balance.  If a manufacturer  accumulates  both 
NOx and PM deficits  from legacy  engines  above  the specified  threshold,  then both NOx 
and PM balances  must  be offset  at four times  the normal  rate. If a manufacturer  only 
accumulates  NOx deficits  from legacy  engine  sales  above  the specified  threshold  with 
no PM deficits , then the manufacturer  would  only need  to offset  the NOx deficits  at four 
times  the normal  rate. If a manufacturer  only accumulates  PM deficits  from legacy  
engine  sales  above  the specified  threshold  with no NOx deficits,  then the manufacturer  
would  only need  to offset  the PM deficits  at four times  the normal  rate.
2.In subsection  1956.8 (a)(2)(C)3.b.iv.2. C, the text was modified  to further  clarify  the intent  
of the regulations  for manufacturers  that use Option  2. The new language  states  that4the excess  NOx and PM emissions  from this percentage  of heavy -duty legacy  engines  
exceeding  the allowable  legacy  engine  sales  limits  must  be offset  at 4 times  the deficit  
balance.  If a manufacturer  accumulates  both NOx and PM deficits  from legacy  engines  
above  the specified  threshold,  then both NOx and PM balances  must  be offset  at four 
times  the normal  rate. If a manufacturer  only accumulates  NOx deficits  from legacy  
engine  sales  above  the specified  threshold  with no PM deficits , then the manufacturer  
would  only need  to offset  the NOx deficits  at four times  the normal  rate. If a 
manufacturer  only accumulates  PM deficits  from legacy  engine  sales  above  the 
specified  threshold  with no NOx deficits,  then the manufacturer  would  only need  to 
offset  the PM deficits  at four times  the normal  rate.
3.In subsection  1956.8(d),  a placeholder  is created  for the most  recent  date of 
incorporation  for CARB  staff’s  amended  “California  Exhaust  Emission  Standards  and 
Test Procedures  for 2004  and Subsequent  Model  Heavy -Duty Otto-Cycle  Engines  and 
Vehicles,”  adopted  December  27, 2000.  Since  these  test procedures  were  amended  as 
part of this rulemaking,  the referenced  amendment  date must  be reflected  in the 
California  Code  of Regulations.
4.In subsection  1956.8(j)( 7), the definition  of the family  emission  limit (FEL)  has been  
modified  to provide  more  flexibility  to engine  manufacturers  that certify  legacy  engine  
familie s. Based  on the changes,  manufacturers  can choose  to specify  the FEL value  for 
each  legacy  engine  famil y to either  two or three  decimal  places.  For example,  a 
manufacturer  can specify  a PM FEL of 0.01 grams  per brake  horsepower -hour 
(g/bhp -hr) or 0.005  g/bhp -hr.
II. 13 CCR  1971.1.  On-Board  Diagnostic  System  Requirements --2010  and Subsequent  
Model -Year  Heavy -Duty  Engines
1.Subsection  1971.1(d)(8.5.1)  currently  states  that manufacturers  electing  to certify  2024,  
2025,  or 2026  model  year heavy -duty engines  to the provisions  of subsection  
1956.8(a)(2)(C)2  may implement  OBD  systems  either  complying  with California  OBD  
requirements  set forth in California  Code  of Regulations  (Cal.  Code  Regs.) , title 13, 
section  1971.1,  or federal  OBD  requirements  set forth in title 40, Code  of Federal  
Regulations  section  86.010 -018, as last amended  January  24, 2023.   The proposed  
amendment  to remove  the option  to certify  to the California  OBD  requirements  from 
subsection  1971.1(d)(8.5.1)  is a necessary  clarification  to maintain  align ment  with the 
requirements  in Cal. Code  Regs.,  title 13, subsection  1956.8(a)(2)(C)2 , which  specifies,  
in pertinent  part, that engines  certifying  under  that subsection  are only required  to 
submit  the federal  certificate  of conformity  demonstrating  those  engines  comply  with all 
federal  requirements  (including  federal  OBD  requirements ).  
III. California  Exhaust  Emission  Standards  and Test Procedures  for 2004  and 
Subsequent  Model  Heavy -Duty  Diesel  Engines  and Vehicles
1.In subparagraph  I.2.B, CARB  staff proposes  to modify  the definition  of California  sales  
volume  by removing  the sale to the ultimate  purchaser  clause .  
This proposed  amendment  would  provide  additional  flexibility  to manufacturers  in 
track ing which  products  are sold as new in the California  market  and which  products  are 
sold in other  states.  After  the end of the model  year,  manufacturers  would  submit  the 
required  end-of-year production  reports  to CARB  to identify  the specific  engine s and 
vehicles  that were  sold in California.  CARB  staff would then use all available  tools  such5as the California  Department  of Motor  Vehicle  registration  data, warranty  registration  
data, sales  records  and any other  available  data to verify  the accuracy  of the California  
sales  volume  for each  manufacturer.
2.In subparagraph  I.11.B.5.3.5.2(d)(1),  the text was modified  to further  clarify  the intent  of 
the regulations  for manufacturers  that use Option  1. The proposed  text   explicitly  
indicates  that excess  NOx and excess  PM emissions  from heavy -duty legacy  engines  
exceeding  the allowable  legacy  engine  sales  limits  must  be offset  at 4 times  the deficit  
balance.  If a manufacturer  accumulates  both NOx and PM deficits  from legacy  engines  
above  the specified  threshold,  then both NOx and PM balances  must  be offset  at four 
times  the normal  rate. If a manufacturer  only accumulates  NOx deficits  from legacy  
engine  sales  above  the specified  threshold  with no PM deficits,  then the manufacturer  
would  only need  to offset  the NOx deficits  at four times  the normal  rate. If a 
manufacturer  only accumulates  PM deficits  from legacy  engine  sales  above  the 
specified  threshold  with no NOx deficits,  then the manufacturer  would  only need  to 
offset  the PM deficits  at four times  the normal  rate.
3.In subparagraph  I.11.B.5.3.5.2(d)(2) (iii), the text was modified  to further  clarify  the intent  
of the regulations  for manufacturers  that use Option  2. The proposed  text explicitly  
indicates  that the excess  NOx and excess  PM emissions  from heavy -duty legacy  
engines  exceeding  the allowable  legacy  engine  sales  limits  must  be offset  at 4 times  the 
deficit  balance.  If a manufacturer  accumulates  both NOx and PM deficits  from legacy  
engines  above  the specified  threshold,  then both NOx and PM balances  must  be offset  
at four times  the normal  rate. If a manufacturer  only accumulates  NOx deficits  from 
legacy  engine  sales  above  the specified  threshold  with no PM deficits,  then the 
manufacturer  would  only need  to offset  the NOx deficits  at four times  the normal  rate. If 
a manufacturer  only accumulates  PM deficits  from legacy  engine  sales  above  the 
specified  threshold  with no NOx deficits,  then the manufacturer  would  only need  to 
offset  the PM deficits  at four times  the normal  rate.
IV. California  Exhaust  Emission  Standards  and Test Procedures  for 2004  and 
Subsequent  Model  Heavy -Duty  Otto-Cycle  Engines  and Vehicles
1. In subparagraph  I.2.B,  CARB  staff proposes  to modify  the definition  of California  sales  
volume  by removing  the sale to ultimate  purchaser  clause.
This proposed  amendment  would  provide  additional  flexibility  to manufacturers  in 
track ing which  products  are sold as new in the California  market  and which  products  are 
sold in other  states.  After  the end of the model  year,  manufacturers  would  submit  the 
required  end-of-year production  reports  to CARB  to identify  the specific  engines  and 
vehicles  that were  sold in California.  CARB  staff would then use all available  tools  such  
as the California  Department  of Motor  Vehicle  registration  data, warranty  registration  
data, sales  records  and any other  available  data to verify  the accuracy  of the California  
sales  volume  for each  manufacturer.
In addition  to the modifications  described  above,  additional  modifications  correcting  grammar,  
punctuation  and spelling  have  been  made  throughout  the proposed  changes.  These  changes  
are nonsubstantive.
The modifications  described  throughout  the Notice  do not change  implementation  of the 
regulation  in any way that affects  the conclusions  of the environmental  analysis  included  in the 
Staff Report  because  the proposed  modifications  consist  primarily  of revisions  to provide  more6flexibility  in tracking  compl iance  with the Omnibus  requirements  without  impacting  the 
projected  emissions  benefits  from the Omnibus  regulation  and clarifications  and definitions  that 
do not alter the compliance  responses.  This rulemaking  would  not create  the potential  for any 
new or more  severe  significant  environmental  impacts  which  were  not previously  examined.  
None  of the modifications  has the potential  to increase  emissions  or otherwise  cause  any 
significant  environmental  impacts . While  the continued  availability  of legacy  engines  in 
California  would  allow  for the ongoing  distribution  of higher  emitting  engines,  all excess  
incremental  emissions  from these  higher  emitting  engines  must  be offset  by distribution  of 
heavy -duty zero-emission  vehicles,  distribution  of lower  emitting  heavy -duty engines,  or by 
performing  projects  in disadvantaged  communities.  The net effect  is to maintain  the 2024  
model  year 0.050  gram per brake  horsepower -hour NOx standard  for the overall  heavy -duty 
sector  for 2024  through  2026  model  years, ensuring  no overall  emissions  increases  from this 
sector.  Therefore,  no additional  environmental  analysis  or recirculation  of the analysis  is 
required.
Agency Contacts
Inquiries  concerning  the substance  of the proposed  regulation  may be directed  toDaniel 
Hawelti , Staff Air Pollution  Specialist,  On-Road  Heavy  Duty Diesel  Section , at (951)  542-3195,  
orMitzi Magtoto , Staff Air Pollution  Specialist,  On-Road  Heavy  Duty Diesel  Section,  at (279) 
208-7363 .
Public Comments
Written  comments  will only be accepted  on the modifications  identified  in this Notice.  
Comments  may be submitted  by postal  mail or by electronic  submittal  no later than the due 
date to the following:
Postal  mail:  Clerks’  Office,  California  Air Resources  Board  
1001  I Street,  Sacramento,  California  95814
Electronic  submittal :  https://www.arb.ca.gov/lispub/comm/bclist.php
Please  note that under  the California  Public  Records  Act (Gov.  Code  § 7920.000  et seq.),  your 
written  and verbal  comments,  attachments,  and associated  contact  information  (e.g.,  your 
address,  phone,  email,  etc.) become  part of the public  record  and can be released  to the public  
upon  request.
In order  to be considered  by the Executive  Officer,  comments  must  be directed  to CARB  in one 
of the two forms  described  above  and received  by CARB  no later than the deadline  date for 
public  comment  listed  at the beginning  of this notice.  Only comments  relating  to the above -
described  modifications  to the text of the regulations  shall be considered  by the Executive  
Officer.
If you need  this document  in an alternate  format  or another  language,  please  contact  the 
Clerks’  Office  at (916)  322-5594  or by facsimile  at (916)  322-3928  no later than five (5) 
business  days  from the release  date of this notice.  TTY/TDD/Speech  to Speech  users  may dial 
711 for the California  Relay  Service.
Si necesita  este documento  en un formato  alterno  u otro idioma,  por favor  llame  a la oficina  del 
Secretario  del Consejo  de Recursos  Atmosféricos  al (916)  322-5594  o env?e un fax al (916)  
322-3928  no menos  de cinco  (5) d?as laborales  a partir  de la fecha  del lanzamiento  de este7
aviso.  Para  el Servicio  Telefónico  de California  para Personas  con Problemas  Auditivos,  ó de 
teléfonos  TDD pueden  marcar  al 711.
California  Air Resources  Board
_________________________________
Steven  S. Cliff, Ph.D.
Executive  Officer
Date:  December  6, 2023
Appendices
The energy  challenge  facing  California  is real. Every  Californian  needs  to take immediate  
action  to reduce  energy  consumption.  For a list of simple  ways  you can reduce  demand  and 
cut your energy  costs,  seeCARB’s  website (www.arb.ca.gov).