Cal ID and CVN Detect Programming Modifications

Illegal modifications to a vehicle’s emission controls can dramatically impact the amount of pollution the vehicle generates. This is true not only for modifications to physical components (e.g., air intake, catalytic convertor) but also for modifications to the software controlling the vehicle’s engine controller (e.g., computer). Programming modifications can be detected using the vehicle’s calibration identification (Cal ID) and calibration verification number (CVN), which together uniquely identify the software program installed on the computer. The Cal ID is the name of the program assigned by the vehicle manufacturer. The CVN is a unique numeric code calculated based upon the computer program. Whenever a computer’s program is modified, a new CVN will automatically be generated that will differ from the one originally associated with the Cal ID.

Over the past year, the Bureau of Automotive Repair (BAR) has been extensively studying Cal ID and CVN and working with the California Air Resources Board (ARB), vehicle manufacturers, Smog Check industry representatives, and BAR Advisory Group members to gather input and develop an implementation plan. In accordance with California Code of Regulations, title 16, section 3340.42.2(c)(8), beginning July 2020, BAR will implement Cal ID and CVN checks for most model-year 2000 and newer vehicles as part of the On-Board Diagnostic Smog Check inspection failure criteria. Owners of vehicles identified with unapproved programming modifications will need to restore the computer to either stock or ARB-approved software in order to pass a Smog Check inspection.

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