What are EEPROM and Flash memory used for in automotive ECUs?

EEPROM (Electrically Erasable Programmable ROM) stores small amounts of data that must survive power cycles, like calibration values, adaptive learn values, immobilizer codes, and fault codes. Flash memory stores larger program code and calibration data, enabling ECU firmware updates. Both are non-volatile (retain data without power). EEPROM allows byte-level writing while Flash requires block erasure. Modern ECUs use Flash for code and EEPROM emulation in Flash for learned values.