B3.9, B4.5, and B5.9 Industria [...] Engine Identification Section E - Engine and System Identification Page E-3 NOTE: If the engine dataplate (1) is not readable, the engine serial number (2) can be identified on the engine block above the oil cooler. Cummins® Engine Nomenclature B5.9 The model name provides the following engine data: B = Engine series 5.9 = Displacement in liters.