Diesel engines are a key component in modern transportation and industry due to their durability, energy efficiency, and reliability. Modern diesel engines use advanced fuel injection and air management systems that enable better combustion and reduced emissions. However, due to the complexity of these systems, diagnosing faults is becoming increasingly difficult, requiring the use of new methods and approaches. The motive for writing the thesis is the advancement of technology and the lack of experts for thorough examination of certain engine systems. In the thesis, based on several specific cases, methods for diagnosing diesel engine problems will be discussed and presented.