This paper focuses on the fault diagnosis and elimination of the adaptive cruise control system in new energy vehicles， taking the 2019 BYD Tang EV model as the object， aiming to provide practical fault diagnosis and elimination solutions for the maintenance field of new energy vehicles. During the research process，the working principle of the adaptive cruise control system is analyzed first， and the fault causes are classified into five categories: sensor faults， control faults， software faults， actuator faults， and circuit faults. Then， through a practical case， the fault diagnosis and elimination of a vehicle with failed adaptive cruise control function are carried out， providing technical references for maintenance personnel of new energy vehicles.