The Tesla Fused Car Computer Hardware 4 Service Unit 1800857-S3-J is a genuine OEM service replacement for the advanced onboard computing system powering Tesla’s Hardware 4 (HW4) Autopilot and Full Self-Driving capabilities. This fused unit combines critical processing functions with integrated safety fusing, enabling reliable high-speed data processing for cameras, radar, and vehicle control systems. Designed specifically for Model X and Model S, it maintains full compatibility with Tesla’s latest autonomous driving architecture. This part is intended for service use and should only be installed by a certified technician, as it may require firmware updates and system calibration.