The product described is a 2008 Nissan XTERRA ECM ECU ENGINE COMPUTER MODULE PCM POWER UNIT 8P 4.0L. It is a direct replacement part designed specifically for Nissan vehicles, with interchange part numbers including 590-51779, 23710-ZS23A, and MEC71-100. This module may require additional programming and is designed for the 4.0L engine. It is an essential component of the powertrain electrical system, ensuring proper functionality of the vehicle's engine and transmission.