Abstract: A drive lock includes a security control unit and an engine control unit that is ready for operation only when the engine control unit has received from the security control unit an encoded release code that matches a predetermined reference code. The engine control unit has storage devices into which it can enter a reference code. On receipt of a release code, it checks on whether a reference code is present in the storage devices. If there is a reference code matching the release code, the engine control unit makes itself ready for operation. If there is no reference code, it accepts the release code into the storage devices as the reference code.

Abstract: The invention is directed to a connecting circuit for a potential-free lambda probe having a ground line and a signal line and having an offset voltage source which is connected to the ground line. This offset voltage source raises the potential of the ground line to a pregiven value relative to ground. A ground short is directly detectable in the connecting circuit of the invention in that the potential measured at the signal line drops below the offset voltage. In this way, it is no longer required as in conventional circuits to check for a ground short by enriching the mixture of an engine and to monitor the exhaust gas with the lambda probe.