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LG groups its indoor faults under CH, followed by a number that identifies the circuit. That prefix is specific to LG, which means if you search a CH code and get results about another brand, you are looking at the wrong chart. The number is the useful part: it tells you whether the fault is communication, sensing or the fan.
| Code | What it means | First test |
|---|---|---|
| CH0 | Communication error with the outdoor unit | Interconnecting cable continuity and terminations |
| CH1 | Indoor temperature sensor malfunction | Sensor resistance against measured room temperature |
| CH2 | Indoor humidity sensor malfunction | Sensor output compared against actual humidity |
| CH3 | Indoor fan motor malfunction | Free rotation with power off, then motor supply |
| CH4 | Coil temperature sensor failure | Sensor resistance, then the plug and loom |
Communication faults sound expensive. On an LG split or multi split, the indoor and outdoor units talk over a low voltage cable that runs with the pipework. That cable gets chewed by rodents, strained during renovations, corroded where it terminates, or filled with water where it enters the outdoor unit. Testing continuity and inspecting the terminations costs a fraction of a board and resolves most CH0 codes. Anyone quoting a control board before testing the cable is guessing.
The humidity sensor code appears more often here through summer than in drier climates, simply because the indoor unit is dehumidifying hard for months and moisture finds its way into places it should not. It also gets misdiagnosed as a board fault regularly. The sensor is a low cost part and testing it takes minutes, so it is worth proving before anything expensive is replaced.
Both are sensor faults but they affect different things. CH1 reads the room, so a failure makes the unit misjudge how warm the space is and it will over or under run. CH4 reads the coil, which feeds the defrost and protection logic, so a failure can cause odd cycling or premature shutdowns. Sitting in the same series does not make them the same fault.
Do not keep resetting the system. Do not replace a control board on a CH0 code before the interconnecting cable has been tested. Do not assume a CH code you found on a forum applies to your model series, because LG has changed sensor conventions across generations of equipment.
Stop and call immediately if there is a burning smell, if the safety switch trips every time the unit starts, if water is anywhere near electrical fittings, or if the outdoor unit tries to start and cuts out within seconds. Those need attendance today.
CH0 is a communication error with the outdoor unit. On an LG it is frequently the interconnecting cable, a loose terminal or water in a connector rather than a failed board. That cable should be tested for continuity and the terminations inspected before anyone quotes for control boards.
CH2 is an indoor humidity sensor fault, and it shows up more in Sydney's humid months because that is when the sensor is working hardest and when moisture ingress is most likely. It is worth testing the sensor properly rather than replacing the board on assumption.
CH1 is the indoor air temperature sensor, which reads the room. CH4 is the coil temperature sensor, which reads the refrigerant circuit. A CH1 fault affects how the unit judges room temperature, while CH4 affects defrost and protection logic, so they behave very differently in use.
Not necessarily. CH3 is a fan motor malfunction, which can mean the motor, the control circuit feeding it, or a mechanical obstruction stopping it turning. With the power off, check the blower turns freely first, then test supply to the motor before condemning it.
Reset once to see whether the code returns, because that tells you whether it was transient. Do not keep resetting it. On fan and communication faults, repeated restarts can cause further damage and they hide the pattern that diagnosis depends on.
LG also uses F codes for outdoor unit faults, which are separate from the CH series and point at the outdoor side of the system. If your controller is showing an F code rather than a CH code, the fault is at the outdoor unit, not the indoor head.
Each indoor head has its own sensors and board, so a CH1 to CH4 fault on one head is usually local to that head. A CH0 communication fault can affect more than one because it involves the shared outdoor unit and the wiring between them.
It depends on the fault, the part and the access. Sensors and cables sit at the low end, fan motors and boards higher. We diagnose first and give you a written figure before any work starts, so you are not paying for a guess.
Not in itself. These codes are the system protecting itself and recording why. What matters is the physical symptom alongside it. A burning smell, water near electrics or a safety switch that trips on every start is urgent regardless of which code is showing.
Yes, and we do it regularly. We will also point out anything in the original installation causing repeat faults, such as undersized pipework, a poor drainage fall or a unit that was never commissioned properly.
