Lennox AC Error Codes
Indoor Unit Error Display
Error Codes: Cause
E0: EEPROM parameter error
E1: Indoor/outdoor units communication protection
E2: Zero-crossing signal error
E3: Indoor fan speed out of control
E5: Open or short circuit of outdoor temperature sensor or outdoor unit EEPROM parameter error
E6: Open or short circuit of room or evaporator temperature sensor
E7: Outdoor fan speed out of control
P0: IBM malfunction or IGBT over-strong current protection
P1: Over voltage or too low voltage protection
P2: Temperature protection of compressor top
P4: Inverter compressor drive error
Lennox Split AC Error Codes
F1: Return air temperature sensor open/ short-circuited
P6: Drive board communication error
F2: Evaporator temperature sensor open/ short-circuited
H3: Compressor overheating protection
b5: Indoor unit liquid valve temperature sensor open/short circuited
LP: Indoor and outdoor units unmatched
b7: Indoor gas valve temperature sensor open/ short-circuited
dn: Communication line misconnected or expansion valve error
P7: IPM temperature sensor open/short circuited
E7: Running mode conflict
F3: Outdoor ambient temperature sensor open/ short-circuited
Fo: Pump-down
F4: Outdoor unit condenser mid-tube temperature sensor open/short circuited
C5: Jumper error
F5: Discharge temperature sensor open/ short-circuited
H1: Forced defrosting
E6: Indoor and outdoor communication error
Lc: Compressor start-up failure
PL: DC bus under-voltage protection
E4: High discharge temperature protection
PH: DC bus over-voltage protection
E8: Overload protection
U1: Compressor phase current sensing circuit error
E5: Whole unit over-current protection
HE: Compressor demagnetization protection
P5: Over phase current protection
Hc: PFC protection
H7: Compressor desynchronizing
P8: IPM Temperature Protection
H5: IPM Current protection
L9: Over-power protection
Ld: Compressor phase loss/reversal protection
F0: System charge shortage or blockage protection
F8: Frequency restricted/reduced with whole unit current protection
PU: Capacitor charging error
IPM: Frequency restricted/reduced with
En: Current protection
E1: High pressure protection
F9: Frequency restricted/reduced with high discharge temperature
E3: Low pressure protection
FH: Frequency restricted/reduced with anti-freezing protection
LE: Compressor stalling
F6: Frequency restricted/reduced with overload protection
LF: Over-speeding
EU: Frequency restricted/reduced with IPM temperature protection
PF: Drive board temperature sensor error
E9: Indoor unit full water error
P9: AC contactor protection
E2: Anti-freezing protection
PE: Temperature drift protection
PP: AC input voltage abnormal
Pd: Sensor connection protection
U5: Whole unit current sensing circuit error
U3: DC bus voltage drop error
U7: 4-way valve reversing error
L3: Outdoor fan 1 error protection
H6: Motor stalling
LA: Outdoor fan 2 error protection
U8: PG motor zero-crossing protection
Lennox Air Conditioner Mini Split Error Codes
Lennox MS8 SERIES AC Error Codes
C5: Indoor control jumper is missing
E0: EEPROM failure
EE: EEPROM failure
E1: Communication failure between indoor unit and outdoor unit
E2: Indoor coil freeze protection – All system functions are terminated except indoor fan
E3: Outdoor coil blockage or low refrigerant due to leak
E4: Discharge line temperature protection
E5: Compressor overcurrent protection
E6: Communication failure between indoor unit and outdoor unit
FH: Anti-freezing upper and lower limit range
FO: Indoor coil is gathering refrigerant
F1: Indoor ambient sensor (RT1) open or short-circuited
F2: Indoor coil sensor (RT2) open or short-circuited
F3: Outdoor ambient sensor (RT4)open or short circuit
F4: Outdoor coil sensor (RT3) open or short circuit
F5: Discharge line sensor (RT5) error
F6: Compressor overload limit issue
F8: High current limit issue
F9: Discharge line temperature too high
HC: Power factor correction protection
H1: Defrosting (heat pump only)
H3: Compressor overload protection sensor (CT1.2) malfunction
H4: Compressor high temperature protection
H5: Intelligent Power Module (IPM) module protection
H6: Indoor fan not communicating
LP: Indoor and outdoor unit mismatch
L3: Outdoor DC fan motor malfunction
L9: Power factor protection
PH: High voltage protection
PL: Low voltage protection
Lennox MPA012S4S-1L AC Error Codes
EO: Outdoor EEPROM error
E2: Communication error between outdoor unit and all indoor units
E3: Communication error between outdoor unit main control and IPM control
E4: Temp sensor error
E5: High or Low voltage protection
E8: Outdoor DC fan speed error
F1: Indoor unit #1 coil outlet temp, sensor error
F2: Indoor unit #2 coil outlet temp, sensor error
F3: Indoor unit #3 coil outlet temp, sensor error
F4: Indoor unit #4 coil outlet temp, sensor error
F5: Indoor unit #5 coil outlet temp, sensor error
F6: Indoor unit #6 coil outlet temp, sensor error
P1: High pressure switch open
P2: Low pressure switch open
P3: Outdoor Compressor current overload sensed
P4: High temperature sensed at compressor discharge line
P5: High temperature sensed at outdoor coil
Lpe: Inverter module (IPM) error
Lennox Universal Mini-Split Error Codes
E0: Indoor unit EEPROM error
E1: Communication error between indoor unit and outdoor units
E3: Indoor fan speed error
E4: Indoor Return air temperature sensor error
E5: Indoor coil temperature sensor error
EC: Low refrigerant
EE: High water level alarm
F0: Outdoor current overload sensed
F1: Outdoor ambient temperature sensor error
F2: Outdoor coil temperature sensor error
F3: Compressor discharge temperature sensor error
F4: Outdoor unit EEPROM error
F5: Outdoor unit fan speed error
P0: Inverter module IPM error
P1: High or Low voltage protection
P3: Outdoor unit low temperature lockout
P4: Compressor drive error
P6: Compressor high-pressure or low-pressure switch open