Sensor fault
A code raised when a temperature or pressure sensor reads outside its expected range. The sensor itself is only one possibility: the connector, the harness, and the board input all sit in the same measurement path.
Also called sensor error
What is a sensor fault?
A sensor fault is a code raised when a reading falls outside the range the board expects. The sensor, its connector, the harness, and the board input all sit in the same measurement path.
Sensor fault: how it works
The board applies a known excitation and measures what returns. A break anywhere in that path reads as open circuit, a short anywhere reads as shorted, and a drifted sensor reads as a plausible but wrong temperature. Because the path runs through a plug and a length of harness, a code naming the sensor is really naming the whole measurement chain.
Where you meet the term
- In an intermittent fault that clears on reset and returns later, which is characteristic of a connector rather than a failed component.
- In a fault appearing shortly after other work, where a connector was disturbed and not fully reseated.
- In a coil temperature protection code, where the sensor is healthy and the temperature it reports is genuine.
How to check it
- Note whether the fault is constant or intermittent. A code that appears and clears points at a connection. A code present from the moment of power-up points at an open or shorted path. Owner check
- Measure at the board plug, not at the sensor. Reading resistance where the harness lands on the board tests the sensor and the wiring together. Repeating it at the sensor itself says which half of that path is at fault. Technician
- Inspect the harness route and the pins. Follow the harness for pinch points at panel edges and for a plug that has been disturbed by earlier work. Both produce a code that comes and goes. Technician
Sensor fault: what it is not
- A sensor fault does not mean the sensor failed. It means the measurement path did not return a valid value.
- A sensor code is an instruction to check the condition being reported, not a parts order. The extreme value may be real.
- Replacing a sensor without inspecting its connector can leave the same code with a new part fitted.
Sensor fault questions
Why does my sensor fault come and go?
Intermittent behaviour points at a connection rather than at a component. A pin making poor contact reads correctly when the plug happens to sit right and fails when vibration or temperature moves it.
Can I replace a sensor myself?
It means opening the indoor or outdoor unit, working near live terminals, and identifying the correct part by model. That places it on the technician side even where the sensor itself is a low cost part.
Does a sensor fault stop the system?
It depends on which sensor. A board that has lost a reading it depends on for protection stops rather than running blind, while a less critical sensor can leave the system running with reduced function.
Where this definition comes from
Written from manufacturer support article, service manual material held in the HVAC Bench evidence record. Where a document limits a definition to certain models, that limit is repeated here rather than generalised across a brand.
- E1, EL 01, or EL01 Error CodesDiscontinued Quantum WYS, CYB, RYB, UYB, and FYB series plus listed companion models.
- 15 and 19 Series Service ManualDaikin 15 and 19 Series units documented in service manual SiUS041501E.
- E1 or E2 Error CodesListed Diamante Essenza, Diamante Pro, Quantum Fresh, Hyperformance, and Ultra systems.