What is the sensor reference voltage that says a "circuit/open"?

Answer by  Sockless (528)

Depending on what you are probing, it means that something is not connected or a circuit is broken somewhere due to damage. Electricity needs a complete (closed) circuit to operate and an incomplete (open) circuit will prevent proper functioning. Check to make sure all wires and connectors are solidly attached and there is no damage to components.

Answer by  Brandon55 (1719)

Voltage is only a difference in potential between two points. A circuit can be "open" or not connected and still read a voltage at two points. If instructions are telling you to check voltage, it is just to see if power and a ground is connected to an open circuit.