Genuine OEM Audi Diesel Engine Control Unit, part number 05L906027BL. This electronic control unit (ECU) is the brain of the diesel engine, responsible for managing fuel injection, ignition timing, and emissions control systems. It is typically located within the engine bay. The unit weighs approximately 0.989 kg and measures 0.21m x 0.185m x 0.04m. Genuine OEM ECUs are critical for ensuring the correct firmware and sensor calibration, which directly impacts engine performance, fuel economy, and emissions compliance.