FMEA

FMEA stands for Failure Mode and Effects Analysis. A failure mode is the way an item can fail — for example a sensor drifting or a connector opening — and the effect is the consequence at component, system or vehicle level. In automotive, the two main variants are Design FMEA (DFMEA) for products and Process FMEA (PFMEA) for manufacturing processes.

FMEA is a qualitative risk analysis that ranks failure modes and drives improvement actions, while FMEDA (Failure Mode, Effects and Diagnostic Analysis) is quantitative. FMEDA adds failure rates and diagnostic coverage to calculate the ISO 26262 hardware metrics — single-point fault metric, latent fault metric and the probabilistic metric for random hardware failures — expected from ASIL B upward.

RPN (Risk Priority Number, severity × occurrence × detection) is still used in many industries, but the 2019 AIAG & VDA FMEA Handbook replaced it for automotive with Action Priority (AP). AP tables rate each severity–occurrence–detection combination as high, medium or low priority, weighting severity first, so a severe failure mode cannot hide behind a low multiplied score.