A method for operating a hybrid drive train of a vehicle

The invention relates to a method for operating a hybrid drive train of a vehicle in which an internal combustion engine (VM) and an electric machine (EM), each individually or after operating situation together drivingly on a vehicle transmission (GE) act with switchable translations, wherein the combustion engine (VM) and the electric machine (EM) via a controllable separating element (K0) are separably coupled to each other or different, and in which, starting from an electric motor driving a drag start of the internal combustion engine (VM) by means of the electric machine (EM) or a Zustart of the combustion engine (VM) by means of a separate starting device (ZS) takes place. For the coordination of circuits of the vehicle transmission (GE) and a required trailing starts or Zustarts of the combustion engine (VM) is provided that, with a running gear shift of the vehicle transmission (GE) and the presence of a request for a drag start or a Zustart of the combustion engine (VM) will vary depending on whether the shift is an upshift, a downshift, a Zugschaltvorgang or a thrust shift, as well as depending on the type of the requested start of the engine (VM) is first a check is made as to whether the switching operation is performed, at least partially executed or aborted to drag before the start or the Zustart is carried out, and that depending on appropriate actions necessary to continue, for at least partial execution or termination of the switching process initiated by the result of this test.