Unique Calibration

Position 4 - Unique calibration is explained in the following:

The Emissions/CAFE/CO2 Compliance Department is responsible for assigning calibration numbers. Unique calibration IDs are assigned to similar vehicles for differentiating between tires, drive configurations, final drive ratios and other certification-significant factors.

These two characters are chosen by the analyst to provide identifiable information unique to each calibration. For example, using the number 2 to denote a two-valve engine versus using a 4 to denote a four-valve engine, provides an easily identifiable difference.