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. 

CARB is actively certifying OBD test tools for J1979-2 vehicles. Starting in spring 2027, J1979-2 vehicles must pass OBD testing using certified OBD test tools to comply with CTC vehicle testing requirements. Please follow the due dates shown in your account to remain compliant. Vehicles may submit tests no more than 90 days prior to the vehicle’s compliance deadlines.

CARB will update the webpage when certified tools are available for sale (https://ww2.arb.ca.gov/our-work/programs/inspection-and-maintenance-program/obd-test-devices).