California Air Resources Board

California regulations prohibit the conversion of emission-controlled vehicles to operate on an alternative fuel, such as natural gas or propane, unless the conversion has been evaluated and certified by the California Air Resources Board (CARB). If the conversion is done before the legal title has been transferred to an ultimate purchaser the conversion manufacturer is considered the Original Equipment Manufacturer (OEM) and must comply with CARB’s new vehicle or engine certification requirements. Conversions done after the legal title has been transferred are considered in-use conversions and must comply with CARB’s alternative fuel retrofit system certification procedures.

Here are CARB's new and in-use on-road vehicle and engine emission-related regulations and test procedures that manufacturers are required to follow to obtain an alternative fuel conversion certification. Manufacturers are strongly encouraged to contact the appropriate certification section prior to submitting an application to schedule a pre-certification meeting to assist them in determining the requirements specific to their application.

Regulations and Test Procedures for New Vehicle and Engine Manufacturers

For new light, medium, and heavy-duty on-road alternative fuel conversion certifications, the following regulations and test procedures apply. These procedures are the same as for an OEM.

• New Vehicle and Engine Certification
  • On-Road Light-Duty Emissions Certification Requirements
  • On-Road Heavy-Duty Certification Program

Regulations and Test Procedures for In-Use Vehicle and Engine Manufacturers

For in-use light, medium, and heavy-duty on-road alternative fuel conversion certifications the following regulations and test procedures apply.

• Alternative Fuel Retrofit Systems (Aftermarket)
  • Title 13, California Code of Regulations, Sections 2030 and 2031
  • Amended Test Procedures 1994-2003 Model Year 
  • New Test Procedures 2004-subsequent Model Year
  • 1993 and earlier certification and installation procedures for certifying retrofit systems designed to convert vehicles to operate on natural gas, propane, or alcohol fuels

Background

On August 14, 2012  CARB conducted a public workshop to discuss current alternate fuel conversion requirements for new and used vehicles and engines used in such vehicles. See

• Mail-out MSO #2012-02, Public Workshop to Discuss Current Alternative Fuel Conversion Requirements for New and Used Vehicles and Engines used in Such Vehicles
  • Workshop Slide Presentation
• Mail-Out MSO #2013-03, Public Workshop To Discuss Newly Approved Alternative Fuel Retrofit System Certification Procedures for In-Use Vehicles and Engines
  • Workshop Presentation, Certification Procedures For 2004 And Subsequent Model Year In-Use Vehicles And Engines 
  • Workshop Presentation, OBD II Specific
  • Summary of California and U.S. EPA certification requirements for new and aftermarket alternative fuel conversions. 

In September, 2014 CARB amended the certification procedures for 1994 through 2003 model years alternative fuel conversion kits, and adopted new certification procedures for 2004 model year and later alternative fuel conversion kits. These amendments are in Title 13, California Code of Regulations, Sections 2030 and 2031 and incorporated test procedures reposted from above for clarity.

• Title 13, California Code of Regulations, Sections 2030 and 2031
• Amended Test Procedures 1994-2003 Model Year 
• New Test Procedures 2004-subsequent Model Year

Contacts

For more information regarding new on-road light-duty alternative fuel conversion certification, please email the On‑Road Light-Duty Certification Program.

For more information regarding new on-road heavy-duty alternative fuel conversion certification, please email the Compression-Ignition and Heavy-Duty Certification Program.

For more information regarding in-use alternative fuel conversion certification, please email CARB's help line.