A method for monitoring and diagnosing errors of drive train components of a motor vehicle by monitoring a transmission route of a drive train control signal by reading an actual value of a monitored output signal at an output of the transmission route of the drive train control signal, determining by a calculation algorithm a nominal output value corresponding to the monitored output signal resulting from a check variable inserted into the transmission route before the output of the transmission route wherein the calculation algorithm is selected such that the nominal output value represents a value of the monitored output signal for the current value of the check variable, and performing a plausibility check of the monitored output signal by determining whether the actual output value is within an acceptable value of the nominal output value for the current value of the check variable.