An apparatus is provided for detecting fault conditions in the energy supply of a load. The apparatus comprises a fail-safe input-output (I/O) module circuit and a diagnostic circuit coupled to the fail-safe input-output (I/O) module circuit. The fail-safe input-output (I/O) module circuit includes a first switch coupled to a first resistor divider and a first output that supplies a DC supply voltage to the load via a first wiring to reduce a first voltage of the first output down to a first readback diagnostic output and a second switch coupled to a second resistor divider and a second output that supplies the DC supply voltage to the load via a second wiring to reduce a second voltage of the second output down to a second readback diagnostic output. The diagnostic circuit is to provide a first readback measurement signal from the first readback diagnostic output and provide a second readback measurement signal from the second readback diagnostic output. The apparatus is configured to provide the first readback measurement signal and the second readback measurement signal for the first output and the second output with and without the load such that when the first and second switches are open or OFF the first voltage at the first output with the load and the second voltage at the second output with the load indicate a NOT broken wire condition with respect to the first and second wirings while the first voltage at the first output without the load and the second voltage at the second output without the load indicate a broken wire condition with respect to the first and second wirings.