California smog check will now look for modified ECU software

Starting this month, California's smog check inspection is specifically going to look for modified engine-control software. OEM and CARB-approved aftermarket ECU tunes should be OK, but vehicles found to have unapproved ECU software will fail. According to the CA.gov website: "Beginning July 19, 2021, vehicles with software not provided by the original equipment manufacturer (OEM) or approved through a California Air Resources Board (CARB) Executive Order (EO) will fail smog check."

Note that the mere presence of non-conforming software is enough to fail. The inspection does not have to prove that the non-conforming software results in higher emissions levels. However, not all aftermarket software is non-conforming. Some ECU tuners have been able to get approval of their software from CARB.