eSys, short for "Electronic System Integration," is a software tool developed by BMW to diagnose, program, and configure various control units within a vehicle. eSys allows technicians and enthusiasts to access and modify vehicle settings, effectively "coding" the car to perform specific functions or enable hidden features.

: Customises your car to your exact preferences for free (minus the cable cost). Efficiency

He bought a standard ENET cable and downloaded the software. That was his first mistake—thinking the software was just "software."