Cause
Open circuit in module wiring
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.
Typically a moderate job.
Codes this can cause (14)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0802 Transmission Control System Malfunction Indicator Lamp Request Circuit/Open Likely for this code Moderate
- P0859 Traction Control Input Signal High Likely for this code Moderate
- P0862 Gear Shift Control Module A Communication Circuit High Likely for this code High
- P0866 Transmission Control Module Communication Circuit High Likely for this code High
- P0899 Transmission Control System Malfunction Indicator Lamp Request Circuit High Likely for this code Moderate
- P2611 Air Conditioning Refrigerant Distribution Valve A Control Circuit/Open Likely for this code Low
- P2613 Air Conditioning Refrigerant Distribution Valve A Control Circuit High Likely for this code Low
- P2668 Fuel Mode Indicator Lamp Control Circuit Likely for this code Low
- P2675 Air Cleaner Inlet Control Circuit/Open Likely for this code Low
- P2677 Air Cleaner Inlet Control Circuit High Likely for this code Low
- P2678 Coolant Degassing Valve Control Circuit/Open Likely for this code Moderate
- P2680 Coolant Degassing Valve Control Circuit High Likely for this code Moderate
- P2681 Engine Coolant Bypass Valve A Control Circuit/Open Likely for this code Moderate
- P2683 Engine Coolant Bypass Valve A Control Circuit High Likely for this code Moderate
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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