LG Aircon CH31 Error Code & Blinking Light: Sensor Checks

What does LG CH31 mean?

LG CH31 is listed as current-to-current transformer thermistor is too low and current to the current-transformer thermistor too low in Wall-Mounted Split rows such as HSV4 / HSV5 single-zone wall-mounted systems, LS091HSV / LS121HSV wall-mounted single-zone. This meaning comes from the manufacturer's own diagnostic material. Do not collapse this code across model families; use the model, series, or system type to choose the right row. Confirm the exact model, series, or signal row before accepting a parts quote.

Choose the listing that matches your unit

The same code has more than one listed meaning. Match the model family, the system type and the unit that shows the code before approving parts.

Code, what it means, and what to check first
Code	What it means	What to check first
HSV4 / HSV5 single-zone wall-mounted systems	Current-to-current transformer thermistor is too low	Match this meaning to your installed model and the unit that shows the code, then use the checks below.
LS091HSV / LS121HSV wall-mounted single-zone	Current to the current-transformer thermistor too low	Match this meaning to your installed model and the unit that shows the code, then use the checks below.

Code
HSV4 / HSV5 single-zone wall-mounted systems
What it means
Current-to-current transformer thermistor is too low
What to check first
Match this meaning to your installed model and the unit that shows the code, then use the checks below.
Code
LS091HSV / LS121HSV wall-mounted single-zone
What it means
Current to the current-transformer thermistor too low
What to check first
Match this meaning to your installed model and the unit that shows the code, then use the checks below.

What to do now

Use these steps before customer action, a sensor check, or PCB quote.

Stop using the unit if CH31 returns
If CH31 remains displayed or returns during operation, do not attempt a reset the manufacturer does not list; arrange diagnosis.
No manufacturer reset steps listed for CH31
Capture the complete CH31 pattern and model stickers first. The manufacturer lists no customer reset procedure; do not treat a generic power-cycle as manufacturer guidance.
Send these to us
CH31 error code and blinking light, a clear display photo and blinking-light video if the unit shows one, LG model stickers, affected rooms, operating state when the code appeared, and when the fault appears

Guidance for your model

Notes that match the code to your exact model. Electrical, refrigerant, wiring, resistance and component checks are for a technician.

Guidance for your model
Detail	What it says
Diagnostic note	Record CH31 and arrange outdoor current-sensing thermistor and PCB diagnosis.
Diagnostic note	Record the exact code and LED blink pattern before booking diagnosis. For LS091HSV / LS121HSV systems, this pattern points to: Current to the current-transformer thermistor too low
Singapore / model note	Official LG HVAC HSV4 / HSV5 wall-mounted self-diagnosis table. Use this row only for matching single-zone wall-mounted systems.
Singapore / model note	Use this LS091HSV / LS121HSV LED table only when the installed model or service manual matches this standard wall-mounted single-zone family.

Detail
Diagnostic note
What it says
Record CH31 and arrange outdoor current-sensing thermistor and PCB diagnosis.
Detail
Diagnostic note
What it says
Record the exact code and LED blink pattern before booking diagnosis. For LS091HSV / LS121HSV systems, this pattern points to: Current to the current-transformer thermistor too low
Detail
Singapore / model note
What it says
Official LG HVAC HSV4 / HSV5 wall-mounted self-diagnosis table. Use this row only for matching single-zone wall-mounted systems.
Detail
Singapore / model note
What it says
Use this LS091HSV / LS121HSV LED table only when the installed model or service manual matches this standard wall-mounted single-zone family.

What to check before repair

Use this split to separate safe evidence capture from the tests a technician should prove before quoting parts.

Homeowner checks and technician confirmations
You can check	Technician should confirm
Before taking any system action on CH31, take a clear display photo and blinking-light video if the unit shows one.	Confirm which sensor CH31 maps to on the exact model table.
Capture the LG indoor and outdoor model stickers so the correct family row is used.	Measure the sensor value against the service-manual resistance or voltage range.
The manufacturer lists no customer reset procedure for this code. Note whether one room, several rooms, or the whole system is affected.	Check connector condition, harness continuity, and PCB input before replacing boards.

You can check
Before taking any system action on CH31, take a clear display photo and blinking-light video if the unit shows one.
Technician should confirm
Confirm which sensor CH31 maps to on the exact model table.
You can check
Capture the LG indoor and outdoor model stickers so the correct family row is used.
Technician should confirm
Measure the sensor value against the service-manual resistance or voltage range.
You can check
The manufacturer lists no customer reset procedure for this code. Note whether one room, several rooms, or the whole system is affected.
Technician should confirm
Check connector condition, harness continuity, and PCB input before replacing boards.

Sensor or PCB decision

LG CH31 is usually repair-first if a sensor or harness reading is confirmed. Board replacement should wait until the sensor circuit is tested.

Sensor replacement is usually targeted when resistance or voltage readings are out of range.
Harness or connector damage can look like a sensor fault until continuity is checked.
PCB replacement is a later step if the sensor and wiring test correctly.

LG CH31 questions

What does the LG CH31 error mean?

LG CH31 is listed as current-to-current transformer thermistor is too low and current to the current-transformer thermistor too low in Wall-Mounted Split rows such as HSV4 / HSV5 single-zone wall-mounted systems, LS091HSV / LS121HSV wall-mounted single-zone. This meaning comes from the manufacturer's own diagnostic material. Do not collapse this code across model families; use the model, series, or system type to choose the right row. Confirm the exact model, series, or signal row before accepting a parts quote.

Can I fix a LG CH31 error myself?

No. CH31 needs a technician's measurement before parts are decided. Before taking any system action on CH31, take a clear display photo and blinking-light video if the unit shows one. Capture the LG indoor and outdoor model stickers so the correct family row is used.

Is it safe to keep running the aircon with a CH31 error?

If CH31 remains displayed or returns during operation, do not attempt a reset the manufacturer does not list; arrange diagnosis.

What causes a LG CH31 error?

LG CH31 has a listed meaning that depends on the exact model and on which unit shows the code. Use the decoder on this page before assuming a specific cause.

Will a LG CH31 error need a repair or a full replacement?

LG CH31 is usually repair-first if a sensor or harness reading is confirmed. Board replacement should wait until the sensor circuit is tested.

What should I send a technician about a LG CH31 error?

Before booking, send: CH31 error code and blinking light, a clear display photo and blinking-light video if the unit shows one, LG model stickers, affected rooms, operating state when the code appeared, and when the fault appears.

Confirm the fault

Share the error code, model number and symptoms so we can assess the likely cause.

Not the right code?

Browse the full LG list or check a few codes in the same fault category.