Unique Calibration
The Emissions/Corporate Average Fuel Economy/Carbon Dioxide Compliance Department is responsible for assigning these calibration numbers. Unique calibration identifications are assigned to cover similar vehicles to differentiate tires, drive configurations, final drive ratios and other calibration-significant factors.
These 2 characters are chosen by the analyst to provide identifiable information unique to each calibration. For example, using the number 2 to denote a 2V engine versus using the number 4 to denote a 4V engine, offers an easily identifiable difference.