A lane controller system installed on a vehicle may include components for self-diagnosing malfunctions on the vehicle. The system may include a desired path generator for generating a desired path that keeps the vehicle within a road lane; a steering controller for providing steering a steering correction to keep the vehicle within the road lane; a vehicle state estimator for estimating the state of the vehicle; a lane marking detector for detecting position of road lane markings; a path predictor for predicting a path actively followed by the vehicle; a virtual dynamics module for modeling the anticipated path of the vehicle following input of the steering controller; a comparer that compares the results of actual steering corrections applied with those predicted by the virtual dynamics module, and a diagnostic system that determines a root cause of malfunctions, based on the comparison by the comparer.