1. A method of operating an engine of a motor vehicle, the method comprising: obtaining, by processing circuitry, inputs identifying whether a braking request is present and identifying driver-input drive requests; cyclically performing, by the processing circuitry, an acceleration monitoring that includes checking whether there is an unintentional acceleration of the motor vehicle, wherein the acceleration monitoring is performed by executing an algorithm that: defines to determine whether the unintentional acceleration is present using a primary check based on signals of a first sensor that indicates a longitudinal acceleration of the vehicle when no fault is detected in the first sensor and its output signals, and without using a secondary check; defines to determine whether the unintentional acceleration is present using the secondary check based on signals of a second sensor in response to satisfaction of a first condition that (a) a fault is detected in the first sensor or its output signals and (b) the inputs indicate that the braking request is present; defines to determine whether the unintentional acceleration is present using the secondary check in response to satisfaction of a second condition that (a) the fault is detected in the first sensor or its output signals and (b) the inputs indicate that an identified driver-input drive request is below a predefined threshold value; defines to determine whether the unintentional acceleration is present using the secondary check in response to satisfaction of a third condition that (a) the fault is detected in the first sensor or its output signals and (b) an unintentional acceleration is indicated to be present by the primary check using a substitute vehicle longitudinal acceleration value that is obtained by reconstructing the longitudinal acceleration of the vehicle using a signal of a third sensor; and defines that the unintentional acceleration is not present, independent of the secondary check, in response to a combination of (a) the fault being detected in the first sensor or its output signals, (b) no braking request being indicated to be present by the inputs, (c) the identified driver-input drive request not being below the predefined threshold value, and (d) the unintentional acceleration being indicated not to be present by a result of the primary check using the substitute vehicle longitudinal acceleration value; and modifying, by the processing circuitry, an operation of the engine in response to a result of the acceleration monitoring being that the unintentional acceleration is present.