Determining a vehicle health status includes sending a request to a gateway device to initiate a diagnostic test for a vehicle network. The request includes an instruction to measure, for a predefined period of time, a voltage produced by the gateway device. The vehicle health status is further determined by converting the request to a probe signal, and asserting the probe signal at differential bus lines of the vehicle network. The health status is further determined by measuring, for the predefined period of time, a voltage at a high level bus line and a voltage at a low level bus line of the differential bus lines, calculating a difference between the voltage measured at the high level bus line and the voltage measured at the low level bus line, and comparing the difference to a predetermined norm voltage value, the results of which indicate the health status.