The penetration rate of new energy vehicles has been increasing year by year, but fuel commercial vehicles still hold a significant position in their respective niche markets. The engine ECU plays a crucial role in fuel economy, power performance, and the overall electronic control functions of the vehicle. However, during the development process, vehicle manufacturers often adopt the method of direct installation and debugging, without conducting system-level integration and debugging of the ECU and the vehicle's electrical system. This paper builds a vehicle electrical system and ECU joint debugging bench based on the engine ECU simulation equipment, conducts simulation tests, and studies and summarizes 24 ECU test items related to electronic and electrical systems, including ECU cruise control, throttle interlock, intake air heating and other functions, to expand the functions of the vehicle electronic and electrical test bench and reduce test costs.