دائرة مفتوحة في أسلاك الوحدة

A break in the wiring between a control module and something it drives or reads — a severed conductor, a terminal that has backed out of its housing, or a connector not mated.

The reason it appears on so many codes is that a module cannot tell an open circuit from a device that is not there. It applies a voltage, measures what comes back, and reports the circuit as out of range. That is the same reading it would get from a failed component, which is why an open circuit is the thing to exclude before buying the part a code names.

Where the break is follows from the loom rather than from the circuit. Conductors do not fail in the middle of a protected run; they fail at the ends and at the points of stress — where a loom crosses a bracket or a heat shield, where it flexes between the body and the engine, at a splice, and in the connector itself. A terminal that has lost tension or pushed back into its housing looks perfectly connected from outside, which is why an unlatched or half-seated plug is found so often after somebody finally unclips it and looks.

The most useful question is what was disturbed recently. A great many open circuits are made rather than grown: a connector unplugged for access to something else, a loom trapped as a cover went back on, a pin pushed out during a probe. A code appearing shortly after unrelated work is that until proven otherwise, and checking costs nothing.