DAIKIN ERROR CODES
Data Verified: January 2026
Professional diagnostic codes and troubleshooting steps.
Critical Severity
A0-11
Refrigerant Leakage Detected (A2L / R-32)
Troubleshooting Steps
- • A2L SAFETY: The system has detected a gas leak. The indoor fan will automatically run at ultra-high speed.
- • Evacuate the area and provide natural ventilation.
- • Check for the use of aerosols, hairsprays, or cleaners near the unit which can cause false trips.
- • Contact a technician to perform a leak test with an A2L-certified detector.
Source Reference Daikin Service Manual
High Severity
A1
Indoor Unit PCB Malfunction
Troubleshooting Steps
- • Check for external electronic noise (EMI) interfering with the board.
- • Verify all connectors on the indoor PCB are seated correctly.
- • If power cycling does not clear the code, the indoor PCB likely needs replacement.
Source Reference Daikin Service Manual
Medium Severity
A3
Drain Level Control System Malfunction
Troubleshooting Steps
- • Check for a clogged condensate drain pipe.
- • Verify the drain pump is operational and receiving power.
- • Inspect the float switch for debris or a 'stuck' up position.
Source Reference Daikin Service Manual
High Severity
A6
Fan Motor Lock / Overload
Troubleshooting Steps
- • Check the indoor fan wheel for physical obstructions (dust buildup or debris).
- • Inspect the wiring harness between the fan motor and the PCB.
- • Verify if the motor rotates freely by hand; if not, replace the motor.
Source Reference Daikin Service Manual
Normal Severity
A7
Swing Flap Motor Malfunction
Troubleshooting Steps
- • Check the horizontal/vertical louvers for obstructions.
- • Verify the connection of the swing motor lead wire.
- • Inspect the limit switch inside the louver assembly.
Source Reference Daikin Service Manual
Normal Severity
AF
Humidifier System Malfunction
Troubleshooting Steps
- • Check for water leakage in the humidifier assembly.
- • Verify the humidifier thermistor and solenoid valve are functional.
- • Inspect the drainage pipe from the humidifier for clogs.
Source Reference Daikin Service Manual
Medium Severity
C4
Liquid Pipe Thermistor Malfunction
Troubleshooting Steps
- • Check the resistance of the heat exchanger liquid pipe thermistor.
- • Inspect for a loose connection at the indoor unit control board.
- • Replace the thermistor if it is shorted or open.
Source Reference Daikin Service Manual
High Severity
E1
Outdoor Unit PCB Malfunction
Troubleshooting Steps
- • Check for loose connections or burnt components on the outdoor main control board.
- • Verify that the green LED on the board is flashing (indicating power).
- • Inspect for moisture or insect nests behind the control box cover.
Source Reference Daikin Service Manual
High Severity
E5
Inverter Compressor Start-up Error
Troubleshooting Steps
- • Check for a seized compressor or 'locked rotor'.
- • Verify all three phases of the compressor wiring (U, V, W) are secure.
- • Ensure the outdoor unit power supply is stable and not dipping during start-up.
Source Reference Daikin Service Manual
High Severity
E7
Outdoor Fan Motor Malfunction
Troubleshooting Steps
- • Check the fan blade for ice buildup or physical obstructions.
- • Inspect the fan motor connector on the outdoor PCB.
- • Measure the resistance of the fan motor windings; replace motor if open.
Source Reference Daikin Service Manual
Normal Severity
H9
Outdoor Air Thermistor Malfunction
Troubleshooting Steps
- • Check the ambient air sensor located on the back of the outdoor coil.
- • Ensure the sensor is not in direct sunlight or near a heat source.
- • Replace the thermistor if it reports impossible temperatures (e.g., -50°F).
Source Reference Daikin Service Manual
Medium Severity
J6
Outdoor Heat Exchanger Thermistor Malfunction
Troubleshooting Steps
- • Inspect the thermistor clipped to the midpoint of the outdoor coil.
- • Check for corrosion on the sensor lead wires.
- • Verify the sensor hasn't fallen off the copper tubing.
Source Reference Daikin Service Manual
High Severity
88
Discharge Pipe Temperature Malfunction
Troubleshooting Steps
- • Check for a shortage of refrigerant gas (leak).
- • Inspect for a clogged refrigerant pipe or closed service valve.
- • Verify the discharge pipe thermistor has proper contact with the line.
Source Reference Daikin Service Manual
High Severity
89
Brazed-Plate Heat Exchanger Freezing
Troubleshooting Steps
- • Check for a dirty heat exchanger or low water flow (if applicable).
- • Inspect for a shortage of refrigerant charge.
- • Verify the freeze protection thermistor is operational.
Source Reference Daikin Service Manual
Medium Severity
C9
Indoor Suction Air Thermistor Malfunction
Troubleshooting Steps
- • Check the return air thermistor located near the intake filter.
- • Verify the sensor is not resting against the metal chassis.
- • Replace the sensor if it reports temperatures outside the range of 32°F-122°F.
Source Reference Daikin Service Manual
High Severity
L5
Inverter Instantaneous Overcurrent (DC Output)
Troubleshooting Steps
- • The inverter detected a surge. Check for a shorted compressor coil.
- • Inspect the power transistor (IPM) for a ground fault.
- • Reset power; if the fault repeats instantly, the compressor may be seized.
Source Reference Daikin Service Manual
Medium Severity
C9
Indoor Suction Air Thermistor Malfunction
Troubleshooting Steps
- • Check the return air thermistor located near the intake filter.
- • Verify the sensor is not resting against the metal chassis.
- • Replace the sensor if it reports temperatures outside the range of 32°F-122°F.
Source Reference Daikin Service Manual
High Severity
L5
Inverter Instantaneous Overcurrent (DC Output)
Troubleshooting Steps
- • The inverter detected a surge. Check for a shorted compressor coil.
- • Inspect the power transistor (IPM) for a ground fault.
- • Reset power; if the fault repeats instantly, the compressor may be seized.
Source Reference Daikin Service Manual
High Severity
J3
Discharge Pipe Thermistor Malfunction
Troubleshooting Steps
- • Check the discharge thermistor resistance (located on the pipe exiting the compressor).
- • Ensure the thermistor is tightly secured with its spring clip and has thermal paste if required.
- • A failing sensor here will prevent the inverter from ramping up to full speed.
Source Reference Daikin Service Manual
Medium Severity
J5
Suction Pipe Thermistor Malfunction
Troubleshooting Steps
- • Inspect the thermistor on the suction line (low-pressure side).
- • Check for moisture ingress into the sensor bulb, which can cause erratic resistance readings.
- • Verify the connection to the outdoor unit main PCB.
Source Reference Daikin Service Manual
High Severity
P4
Inverter Fin Temperature Sensor Malfunction
Troubleshooting Steps
- • The sensor monitoring the inverter heat sink temperature has failed.
- • Check for dust or blockage preventing airflow across the control box heat sink.
- • If the cooling fan is running and the sink is clean, replace the inverter PCB.
Source Reference Daikin Service Manual
High Severity
U0
Refrigerant Shortage / Low Pressure Lockout
Troubleshooting Steps
- • System is low on charge. Perform a leak search on all flare connections.
- • Check for a clogged refrigerant pipe or a partially closed service valve.
- • Verify the Electronic Expansion Valve (EEV) is not stuck closed.
Source Reference Daikin Simple Self-Diagnosis
High Severity
U4
Transmission Failure (Indoor to Outdoor)
Troubleshooting Steps
- • Check the '1', '2', and '3' wiring between the indoor and outdoor units.
- • Ensure the outdoor unit has 240V power (a tripped outdoor breaker often triggers U4).
- • Inspect for burnt components on either the indoor or outdoor PCBs.
Source Reference Daikin Simple Self-Diagnosis
High Severity
UA
Indoor-Outdoor Unit Combination Fault
Troubleshooting Steps
- • The indoor and outdoor units are incompatible in size or model generation.
- • Check the capacity settings on the indoor unit dip switches.
- • Ensure the outdoor unit address is correctly set for multi-zone systems.
Source Reference Daikin Simple Self-Diagnosis