A communications system for a vehicle includes an antenna mounted on a vehicle and configured to communicate with a plurality of remote units. A diagnostic controller is configured to detect obstacles or damage to the antenna. The diagnostic controller is configured to receive remote messages, measure a receive signal strength of the remote messages, and determine a ratio of low receive signal strength sample messages to total sample messages. The diagnostics controller is further configured to trigger a diagnostic output to the vehicle when the ratio is greater than a predetermined threshold.