ECUs (Engine Control Units) control a vehicle's engine functions using software called "calibrations" or "maps" which can be updated for improved performance or to address issues. Some ECUs (that support the OBDII standard) have a Calibration Verification Number (CVN) and Calibration Identification (CALID) to track versions of calibrations.
Calibration Identification (CALID) is an identifier that is used to track the different versions of calibrations. Each calibration (or software version) has a unique CAL ID, and it is used to distinguish between different versions of the same calibration. This is useful for diagnosing issues with the engine and for determining which calibration version is currently loaded onto the ECU. Calibration Verification Number (CVN) is an identifier that is generated upon request by the ECU itself for each calibration. It is based on a mathematical algorithm (or a checksum).
The purpose of the CVN is to verify that the calibration loaded onto the ECU is the correct one and has not been tampered with or corrupted. If the numbers do not match, this can potentially void the vehicle's warranty. Since 2018, numerous countries have integrated the CVN check into their annual car inspections as well. During the inspection, the CVN is cross-referenced with an online database to determine whether the vehicle's software is up-to-date and unaltered. For example, the TÜV in Germany has been rejecting many modified cars during annual inspections since 2018.
To remedy this issue, our CVN Correction service provides a solution by correcting the CVN after a vehicle has been tuned. This allows our performance calibrations to be undetectable by third parties. Do note that while we are happy to perform a CVN Correction for you, we do not offer this service in conjunction with emissions deletes.