Modern automotive manufacturing and after-sale vehicle service environments require tailoring of configuration values or “calibrations” within vehicle electronic control units (ECUs) to a specific vehicle’s option content. Historically, ECU hardware and software limitations have led software designers to implement calibrateable values using opaque binary blocks tied directly to internal ECU software data structures. Such coupling between calibration data files and ECU software limits traceability and reuse across different software versions and ECU variants. However, more and more automotive ECUs are featuring fast microprocessors, large memories, and preemptive, multi-tasking operating systems that open opportunities to object-oriented approaches. This paper presents just such an object-oriented solution to the automotive calibration problem. The CalDef framework uses XML database methods to define, develop, and deliver calibration values as traceable objects in both manufacturing and service environments. To reduce consumption of precious manufacturing network programming time, CalDef defines overlays, called “cal overrides”, wherein only values that are have been changed from their design-time defaults must be programmed into the ECU. This strategy limits consumption of programming network bandwidth and allows Caldef to be deployed in existing automotive manufacturing plant programming environments without programming tool changes. The first section of this paper traces the history of automotive calibrations as the motivation for the CalDef architecture. The System Design section presents the Caldef design while last section provides a brief overview of the CalDefTools software suite that was written to support Caldef definition, development, and production release.