A method for detecting faults in a vehicle control system comprising functional units having an associated unique prime number label is provided. The method comprises calling each of the functional units, the call comprising a readable and updateable integer traversal value, and in case the functional unit is operating correctly, updating the traversal value to be the product of the value in the call and the label of the currently called functional unit, and in the case of a fault, not updating the traversal value. Further, the method comprises determining from the traversal value if any functional units are faulty by a comparison with an expected traversal value, and, in the case that the traversal value is not equivalent to the expected traversal value, determining which functional units are faulty by a unique prime factorization algorithm.