Abstract: A sensor system for detecting impacts to a vehicle, including diagnostics for monitoring the sensor system. The sensor system includes one or more piezoelectric sensor assemblies (42), each including a coaxial piezoelectric cable (44) contained within a tube housing (54), which is mounted to a structural member of the vehicle. The sensor system may also include accelerometers (36, 38) that are also in communication with the restraints control module (40) and employed in combination with one or more piezoelectric sensor assemblies (42). Further, the sensor system includes diagnostics for monitoring one or more of the sensor assemblies (42) in order to detect a sensor failure, while not interfering with the impact signals from the sensor assemblies (42).