Device for checking the integrity of a digital transmission for an analog output of a system. The analog output may be checked for transient errors that can be attributed to a digital transmission path embedded somewhere within the vehicle system. A test signal is introduced into a digital transmission that can be reassembled from an analog path of the analog output, and, if not, allows the test device to pinpoint that errors are appearing due to the digital path, and not because of the analog output. In this way, debugging an installation of a system becomes easier; obtaining confidence in reliability of a mixed analog and digital system becomes less of a challenge and less time consuming.