Functional diagnostics
Grading & ConditionOperations
Functional diagnostics is the automated testing of a device's internal components - battery, camera, sensors, microphone, and connectivity - to determine whether it works as intended, independent of physical appearance.
Functional and cosmetic condition produce separate and often divergent price signals: a device can look pristine but be functionally degraded, or look worn but remain fully functional. Sellers who price only on cosmetic grade without validating functionality systematically misprice part of their inventory. Battery health has become an explicit pricing variable on platforms such as Back Market and Amazon Renewed, and sub-80% battery health typically carries a measurable discount.