PCM Tuner is a diagnostic and programming tool used primarily for ECU (Engine Control Unit) and TCU (Transmission Control Unit) tuning. PCM Tuner tools are popular among automotive professionals for tasks such as remapping, calibration, and unlocking additional vehicle performance features. These tools typically support a wide range of car models and brands, offering various functionalities like reading and writing ECU/TCU data, performing DPF/EGR removal, and tuning files.