A vehicle includes a radar sensor for detecting objects in the vehicle path. The radar sensor may become blocked by contaminants or debris. A controller monitoring the radar system may detect a radar blockage when a return signal magnitude is less than a threshold. A typical response may be to set a radar blockage diagnostic under such a condition. The controller may inhibit setting a radar blockage diagnostic when other data indicates that the radar sensor is not blocked. Data such as vehicle position, traffic information, camera images, and historical radar returns may be used. A controller may confirm a radar blockage diagnostic when other data indicates that the radar sensor may be blocked. Data such as temperature, vehicle position, surface roughness, automated brake interventions, and heating system status may be used. Return signal dependent functions may be operated based on the radar blockage diagnostic.