Samsung Air Conditioner Error Code E291

E291 indicates a high pressure sensor circuit error. The control board has detected that the sensor's output voltage is either below 0.4V, which signals a short circuit, or above 4.2V, which signals an open circuit. Both conditions mean the board cannot get a valid pressure reading from the sensor, so the unit stops operating to protect the compressor and refrigerant circuit.

No, you should not attempt to bypass or ignore this error. The high pressure sensor is a protection device that prevents the compressor from operating under dangerous over-pressure conditions. Running the system without a functioning high pressure sensor could result in compressor damage or refrigerant line failure. Leave the unit off until the fault is diagnosed and repaired.

A power reset may temporarily clear the error code display, but the code will return as soon as the control board detects the out-of-range sensor voltage again. Because the underlying fault is a hardware issue in the sensor circuit, clearing the code without fixing the root cause does not restore safe operation. The sensor wiring and sensor itself must be inspected and repaired before the error will stay cleared.

Some basic checks are accessible to a knowledgeable DIYer, such as inspecting the sensor wiring harness for visible damage and reseating connector plugs. However, testing sensor output voltage and working around the refrigerant circuit and electrical components of a high-voltage system is best left to a qualified technician. If the sensor itself needs replacement, a technician with proper tools and certifications should handle the repair.

Repair costs vary depending on whether the issue is simply a loose connector or requires a replacement sensor or control board. A wiring or connector repair might cost between $75 and $150 in labor. A replacement high pressure sensor typically adds $30 to $80 in parts. If the control board is at fault, total repair costs including parts and labor could range from $200 to $500 or more.