Abstract <p>The reliability and efficiency of equipment depend, among other things, on the operation of the cylinder–piston group (CPG)—the most frequently repaired unit in automotive and tractor engines. The quality of the CPG assembly is ensured by group interchangeability methods (selective assembly). In mechanical engineering, the human-readable marking of parts based on color schemes is insufficiently informative, so it is advisable to move from human-readable to machine-readable marking. In order to implement digital marking for spare parts and digital transformation of repair enterprises, the main quality indicators of CPG spare parts of engines and selective assembly of piston–liner joints of ZMZ-402 engines in 10 groups are considered. To improve the accuracy of the basic assembly conditions when implementing the method of intergroup interchangeability of CPG engines and automate the assembly process, it is proposed to use machine-readable marking based on a QR code or radio frequency tags. The advantages of a QR code are low cost of creation, fast readability of information, the ability to create a redundant QR code, high capacity, and the ability to read several tags simultaneously. Marking using radio frequency tags (RFID, NFC) allows encoding and reading information without direct contact. It is more resistant to mechanical impacts compared to a QR code. Significant disadvantages of radio frequency tags are the difficulty of reading when shielding the signal and the high cost of implementing this marking system. Digital marking of spare parts will help to forecast demand, improve automation, ease of use of warehouse databases and transparency of operations, and more accurately predict the timing and cost of repairs. Using a QR code together with the information environment (Internet catalog) of an enterprise will improve collection during selective assembly and reduce the likelihood of personnel errors.</p>