LG Air Conditioner Error Code E291

E291 on an LG air conditioner indicates either a refrigerant leakage condition or a fault on the high pressure sensor circuit, specifically a short or open circuit. The PCB monitors the high pressure sensor continuously and triggers this code when the sensor signal falls outside acceptable parameters or disappears entirely. The system shuts down to protect the compressor and refrigerant circuit from damage.

No, you should not attempt to bypass or continue operating the unit while E291 is active. The error indicates either a refrigerant leak or a pressure monitoring failure, both of which can lead to compressor damage or unsafe operating pressures if ignored. The system shuts itself down as a protective measure, and running it in this state risks costly additional damage.

A power reset may temporarily clear the E291 code and allow the unit to restart, but if the underlying problem persists, the error will return quickly. A reset alone does not fix a faulty sensor, damaged wiring, or a refrigerant leak. Clearing the code without diagnosing and correcting the root cause can lead to repeated shutdowns and potential compressor damage over time.

Some steps are DIY-friendly, such as inspecting the high pressure sensor connector and reseating it if it has come loose. However, checking the 5V signal between pins 3 and 4 requires a multimeter and basic electrical knowledge. Any work involving refrigerant, including leak detection and recharging, must be performed by an EPA-certified technician, so a full repair often requires a professional.

Repair cost depends heavily on the root cause. A simple connector reseat has no parts cost and minimal labor time. Replacing the high pressure sensor typically runs in the range of $100 to $250 including parts and labor. If refrigerant leakage is involved, leak detection, repair, and recharging can add $200 to $600 or more depending on the severity of the leak and the refrigerant type used in your system.