A possibility has been investigated to diagnose the condition of a cylinder-piston group in the diesel engine KamAZ-740.63-400 for trucks KamAZ-6460 after a 60,000 km run. The following diagnosing parameters have been selected: a crankcase gas pressure, the compression and vacuometric properties of a cylinder-piston group. A special feature of these mated parts is that they maintain the normal combustion process in the diesel engine cylinders, as well as its resource. We have determined the boundary limits for diagnosing a crankcase gas pressure ‒ 2.39‒2.41 KPa. Based on data about the crankcase gas pressure, the examined trucks revealed malfunctions on the runs of 36,000 km, 48,000 km, 60,000 km. Given the rules for assessing the characteristics of compression-related faults, the minimum compression value for the diesel engines was 30.05 MPa or its difference among the cylinders did not exceed 10–12 %. The data on compression helped detect faults after 48,000 km run and 60,000 km run. We have determined the boundaries of wear based on the vacuometric parameters: maximum vacuum – 69–86 KPa; residual vacuum – 26–41 KPa. Control of the vacuometric properties of a cylinder-piston group has revealed faults in the diesel engines over their run interval of 36,000–60,000 km. An entropy approach has been applied to estimate the informativeness of the appropriate diagnosing parameters in bits. The informativeness level of a crankcase gas pressure is 0.329 bits, compression in cylinders – 0.249 bits, vacuometric indicators – 0.582 bits. This study allows the rational formation of the diesel engine condition diagnosing complexes during technical operation, as well determining the prerequisites for malfunctions. The data acquired are important for transportation and service enterprises and companies that manage freight vehicles