This unit describes the skills and knowledge required to diagnose and repair faults in the traction motor speed control systems of battery electric vehicles (BEVs). These systems may be referred to as digital motor controllers (DMCs) or motor control units (MCUs). The unit involves preparing for the task, sourcing a diagnostic testing strategy, diagnosing the cause of the fault, carrying out the repair, performing post-repair testing, and completing workplace processes and documentation. Importance is placed in the unit on applying electrical safety procedures when working on high voltage (HV) rechargeable energy storage systems (RESS).