What is the crankcase? A crankcase is the housing for the crankshaft in the internal combustion engine of a vehicle. In most engines in modern cars today, the crankcase is usually integrated within the engine block. Two-stroke engines usually utilize a crankcase-compression design, causing the fuel and air mixture to pass through the resulting crankcase before entering the engine cylinders. This design of the particular engine means that there is no oil sump within the crankcase or the crankcase pressure sensor. In a vehicle, the crankcase usually forms the lower half of the main bearing journals, with the bearing caps completing the other half. Within the crankcase, you have the crankcase pressure sensor. The main bearing journals that hold the crankcase are the bearings that hold the crankshaft in place and allow it to rotate within the engine. The crankcase pressure sensor is in charge of providing the electronic control module with the right data to keep it working at the right level within the engine crankcase. Since engines produce fumes during the normal running of a car, this means it is absolutely crucial for the electronic control module to be able to obtain an accurate crankcase pressure value and receive one from the crankcase pressure sensor. This correct reading and data given can ensure that the pressure does not get too high and damage the seals and gaskets. This is also crucial for recycling the fumes back into the engine by means of the positive crankcase ventilation system. This all depends on the proper working of the crankcase pressure sensor and the status of the crankcase.