California Air Resources Board

Guidance for Engines Using the SAE J1979-2 (OBDonUDS) Protocol

Heavy-duty vehicle manufacturers that currently use the SAE J1979 communication protocol for OBD certification will transition to the SAE J1979-2 communication protocol starting with the 2027 engine model year. A small subset of Volvo and Mack vehicle models and engine families have begun this transition to the SAE J1979-2 communication protocol early starting with the 2024 model year. 

Vehicle owners should follow the due dates shown in their account to remain compliant. CTC-VIS accounts contain up-to-date testing deadlines and requirements specific to your vehicle(s). You may also check your Monthly Statements for reminders prior to compliance requirements.

CARB is actively certifying OBD test tools for J1979-2 vehicles, and will update the webpage as certified tools become available for sale (https://ww2.arb.ca.gov/our-work/programs/inspection-and-maintenance-program/obd-test-devices).