# ECU **slug:** `ecu` · **URL:** `/knowledge/glossary/ecu/` · **category:** Automotive · **reviewer:** Tatiana ### Definition ECU (Electronic Control Unit) is the umbrella term for an embedded computing module in a vehicle that controls one or more vehicle subsystems. Modern vehicles contain 50-150 ECUs networked together via [CAN bus](/knowledge/glossary/can-bus/), CAN-FD, automotive Ethernet, or specialized buses. ### What it means ECUs include engine control modules (ECM/PCM), transmission control, brake control (ABS/ESC), body control (BCM), airbag control, infotainment (head unit), telematics control (TCU), gateway ECUs, and increasingly autonomous-driving control units (ADCU). Their compute capacity has grown from 8-bit microcontrollers in the 1980s to multi-core ARM SoCs in the 2020s. ECU security testing covers: firmware extraction (often via debug interfaces or chip-off), reverse engineering, communication protocol fuzzing on the bus interfaces, secure-boot chain analysis, and (where applicable) Hardware Security Module (HSM) integration review. Different ECU classes have different attack surfaces — a head unit ECU has wireless attack surface (BLE, Wi-Fi, cellular), while an engine ECU is typically reached only via the in-vehicle network. ### Related terms - [CAN bus](/knowledge/glossary/can-bus/) - [OBD-II](/knowledge/glossary/obd-ii/) - [TARA](/knowledge/glossary/tara/) - [ISO/SAE 21434](/knowledge/glossary/iso-sae-21434/) ### Authoritative sources - [AUTOSAR Classic Platform specification](https://www.autosar.org/standards/classic-platform/) - [SAE J3061 (Cybersecurity Guidebook for Cyber-Physical Vehicle Systems — superseded by ISO/SAE 21434 but historically relevant)](https://www.sae.org/standards/content/j3061/) ---