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We have developed a micromachined mass flow sensor placed on a high pressure stable substrate to measure on board the different injection quantities needed in modern direct injection (DI) systems for optimum performance. To detect the injection end/begin as well as the injection rate as fast and precisely as possible, a flow sensor is for the first time completely integrated into the nozzle body very close to the injection holes. The thermal measurement principle is chosen, as both gasoline and diesel fuel quantities can be detected and therefore, the use of this present flow sensor is not restricted to one of these different types of combustion engines. In this paper, the fabrication process of the first prototypes is reported mainly focusing on the technology for the LTC (Low Temperature Cofired) ceramics.