A fault detection scheme can include use of a relatively high injection impedance between an input port for analog measurements from a sensor and a stimulus generation circuit controlled in coordination with analog measurement. The stimulus generation circuit can provide a stimulus signal through the injection impedance. A magnitude of the injection impedance can be specified relative to a source impedance associated with a source (e.g., a sensor or other device) coupled to the input port. For example, a magnitude of the injection impedance can be specified to be larger than the source impedance or the injection impedance magnitude can be specified to be a multiple of the source impedance.