ECU (Electronic Control Unit)
Workshop glossary › Diagnostics & protocols · UpdatedAny embedded computer in a vehicle. A modern car has 50–150 of them, networked over CAN/CAN FD/Ethernet, each running its own firmware.
ECU is the generic term for any embedded controller in a vehicle. The engine control unit is the most famous one, but a modern car carries between 50 and 150 ECUs — door modules, ABS, transmission control, gateway, infotainment, instrument cluster, battery management on EVs, ADAS controllers, telematics, climate control. Each runs its own firmware on a microcontroller (typically Renesas RH850, Infineon TriCore, or NXP S32K).
From a diagnostic perspective every ECU has a unique address on the network, supports a subset of UDS services, stores its own DTCs, and may need its own coding or calibration after replacement. Replacing a door module on a VW often requires an online coding session against the central server; replacing an ABS module on a Volvo requires bleeding the brake system via the scan tool.