Software Upgrade for Diesel Trucks Program

This page last reviewed May 31, 2011

Regulatory Activities

This page contains regulatory information and documents about the Low NOx Software Upgrade Program.


The Board has approved a regulation requiring owners and operators of most 1993 - 1999 model year heavy-duty diesel trucks, school buses, and motor homes with engines manufactured by Caterpillar, Cummins, Mack/Renault, Volvo, and International to install low NOx  software. Owners of engines manufactured by Detroit Diesel Corporation (DDC) also have an obligation to have low NOx software installed under the Voluntary Software Upgrade Program.  However, if reflash progress is not significant, then owners of DDC engines would also be subject to regulation.  When installed, the low NOx software reduces NOx, a component of smog that can damage lungs.

Regulatory Documents for the Software Upgrade for Diesel Trucks (posted January 9, 2007)

The final rulemaking package was approved by OAL on March 21, 2005 and became effective that same day. A clean copy (without strikeout and underline) is available from the link below.

Final Regulation Order 'clean copy' (pdf - 66K)

December 2004 - Board Hearing Documents
Second Notice of Public Availability of Modified Text (pdf - 10K)
Notice of Public Availability of Modified Text (pdf - 8K)

March 2004 - Board Hearing Documents
(posted February 9, 2004)

NOTE: Comments made in response to the "Notice of Public Hearing to Consider Adoption of the Heavy Duty Diesel Engine Software Upgrade Regulation (Chip Reflash)," dated August 26, 2003, and published September 5, 2003 (California Regulatory Notice Register, Register 2003, No. 36-Z), will be responded to in the Final Statement of Reasons for this rulemaking, for which a notice dated January 27, 2004, was published February 6, 2004 (California Regulatory Notice Register, Register 2004, No. 6-Z), as applicable.

Informational Notice (mailed to vehicle owners/operators) (pdf - 24K)
En Espaņol, Portions of the Informational Notice (pdf - 13K)
Staff Report (pdf - 14K)
Attachment A - Staff Report (for the December 2003 Board Hearing) (pdf - 163K)
Appendix A - Proposed Regulation Order (pdf - 97K)  Note: This language is not being proposed for comment. This language was proposed at the December Board Hearing.
Appendix B - Low NOx Rebuild Program Requirements (pdf - 78K)
Appendix C - Low NOx Software Engine List (pdf - 48K)
Attachment B - Proposed Regulation Order (pdf - 47K)
Attachment C - Descriptive List of Regulatory Text Changes Proposed for the Heavy-Duty Roadside Inspection Program and the Heavy-Duty Vehicle Fleet Inspection Program (pdf - 11K)

Proposed Software Upgrade Program Information
En Espanol - Frequently Asked Questions (pdf - 81K) (added October 1, 2003)
Frequently Asked Questions (pdf - 74K) (updated September 5, 2003)
List of Engines for which Low NOx Software is available (pdf - 8K)

December 2003 - Board Hearing Documents (posted September 5, 2004)
Notice of Change of Location (pdf - 91K) or
October 2003- Public Hearing Notice (pdf - 94K)
Staff Report (pdf - 162K)