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OBD diagnostic and error codes

Each transmission repair starts with the diagnostics. This process includes checking of level and quality of the oil, pressure measurement, stall testing, and computer-aided diagnostics to determine transmission control problems. The electronic control unit ECU (PCM, TCM, ECM) can detect malfunctions by means of reading out and processing the information related to the transmission operation.

Despite the fact that automakers use different types of service equipment and algorithms of methods for detection of transmission control failures, all diagnostic control units operate according to a standard protocol for self-diagnostics named as OBD.

OBD-II (On-board diagnostics) is a standard developed in the mid-1990s which provides specialists with a range of standardized functional capabilities. This standard allows reading out of current parameters, reading, viewing and deleting of embedded error codes, controlling over actuators and also makes it possible to monitor statuses of body parts and additional devices.

Each of OBD- II codes consists of 5 symbols (one letter and four numbers) and can be decoded as follows:

The first symbol is a letter indicating the vehicle system with a malfunction:

The second symbol is a number indicating a standard nature or uniqueness of the error.

The third symbol is a number indicating the type of malfunction

The fourth and fifth symbols correspond to sequence number of OBD codes