How House Works

Lennox furnace codes (E-codes and LED flashes)

103 codes for SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML195*, ML196*E, ML296*V, ML297*V, G71MPP, each with the wording and source from Lennox installation instructions and Unit Information.

By How House Works EditorialBased on Lennox installation instructions and Unit InformationChecked against sources Updated

All Lennox codes

Meanings are quoted from Lennox installation instructions and Unit Information. The "Who" column is our reading of theremedy in those documents: whether an owner can do the first checks, or the fix belongs to a licensed technician.

CodeMeaningSeriesWhoSource
E000“No error in memory”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*V, EL297*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*VTechnician508559-01 p. 27; 508561-01 p. 34; 508585-02 p. 47; 1126-L5 p. 22; 508583-01 p. 50; 508577-02 p. 42; 508575-02 p. 45; 508573-01 p. 44; 508545-01 p. 27; 508547-01 p. 47; 508565-01 p. 41; 508569-01 p. 44; 508521-01 p. 41; 508907-01 p. 45
E105“Device communication problem - No other devices on RS BUS (Communication system).”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician508559-01 p. 27; 508561-01 p. 34; 508585-02 p. 47; 1126-L5 p. 15; 508583-01 p. 50
E105“Device communication problem - No other devices on BUS (Communication system).”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 62; 508589-02 p. 45; 506509-01 p. 65
E106“Twin Communication Fault”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician508575-02 p. 45; 508573-01 p. 44; 508545-01 p. 27; 508547-01 p. 47; 508565-01 p. 41; 508569-01 p. 44
E110“Low line voltage.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 27; 508561-01 p. 34; 508585-02 p. 47; 506610-01 p. 62; 508589-02 p. 45; 1126-L5 p. 15; 1246-L10 p. 12; 508583-01 p. 50; 508577-02 p. 42; 1901-L1 p. 13; 508575-02 p. 45; 508573-01 p. 44; 508545-01 p. 27; 508547-01 p. 47; 508565-01 p. 41; 508569-01 p. 44; 508521-01 p. 41; 508907-01 p. 45; 506509-01 p. 65
E111“Line voltage polarity reversed.”SL280*V, SLP99*V, EL296*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician506763-01 p. 61; 508589-02 p. 45; 1246-L10 p. 12; 1901-L1 p. 13; 508575-02 p. 45; 508573-01 p. 44; 508545-01 p. 27; 508547-01 p. 47; 508565-01 p. 41; 508569-01 p. 44
E111“Low line voltage.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*V, EL297*E, ML296*V, ML297*VTechnician508559-01 p. 27; 508561-01 p. 34; 508585-02 p. 47; 1126-L5 p. 15; 508583-01 p. 50; 508577-02 p. 42; 508521-01 p. 41; 508907-01 p. 45
E112“Ground not detected”SL280*V, SL280*NV, SL297*NV, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*VTechnician508559-01 p. 27; 508561-01 p. 34; 508585-02 p. 47; 1126-L5 p. 15; 1246-L10 p. 12; 508583-01 p. 50; 508577-02 p. 42; 1901-L1 p. 13; 508575-02 p. 45; 508573-01 p. 44; 508545-01 p. 27; 508547-01 p. 47; 508565-01 p. 41; 508569-01 p. 44; 508521-01 p. 41; 508907-01 p. 45
E112“Earth ground not detected”SLP99*VTechnician508589-02 p. 45
E113“High line voltage.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 27; 508561-01 p. 34; 508585-02 p. 47; 506610-01 p. 62; 508589-02 p. 45; 1126-L5 p. 15; 1246-L10 p. 12; 508583-01 p. 50; 508577-02 p. 42; 1901-L1 p. 13; 508575-02 p. 45; 508573-01 p. 44; 508545-01 p. 27; 508547-01 p. 47; 508565-01 p. 41; 508569-01 p. 44; 508521-01 p. 41; 508907-01 p. 45; 506509-01 p. 65
E114“Line voltage frequency out-of-range.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, G71MPPTechnician508559-01 p. 27; 508561-01 p. 34; 508585-02 p. 47; 506610-01 p. 62; 508589-02 p. 45; 1126-L5 p. 15; 1246-L10 p. 12; 508583-01 p. 50; 508577-02 p. 42; 1901-L1 p. 13; 508575-02 p. 45; 508573-01 p. 44; 508545-01 p. 27; 508547-01 p. 47; 508565-01 p. 41; 508569-01 p. 44; 506509-01 p. 65
E115“Low 24V - Control will restart if the error recovers.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, G71MPPTechnician508559-01 p. 27; 508561-01 p. 34; 508585-02 p. 47; 506610-01 p. 62; 508589-02 p. 45; 1126-L5 p. 15; 1246-L10 p. 12; 508583-01 p. 50; 508577-02 p. 42; 1901-L1 p. 13; 508575-02 p. 45; 508573-01 p. 44; 508545-01 p. 27; 508547-01 p. 47; 508565-01 p. 41; 508569-01 p. 44; 506509-01 p. 65
E116“High 24V.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician508245-01 p. 52; 508150-02 p. 45; 1802-L1 p. 16; 1126-L5 p. 15; 100088 p. 38
E117“Poor ground detected (Warning only)”SL280*V, SL280*NV, SL297*NV, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*VTechnician508559-01 p. 27; 508561-01 p. 34; 508585-02 p. 47; 508589-02 p. 45; 1126-L5 p. 15; 1246-L10 p. 12; 508583-01 p. 50; 508577-02 p. 42; 1901-L1 p. 13; 508575-02 p. 45; 508573-01 p. 44; 508545-01 p. 27; 508547-01 p. 47; 508565-01 p. 41; 508569-01 p. 44; 508521-01 p. 41; 508907-01 p. 45
E118“Reset limit exceeded (Hard-Lockout)”SLP99*VTechnician508589-02 p. 45
E120“Unresponsive device. Communication only.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician508559-01 p. 27; 508561-01 p. 34; 508585-02 p. 47; 1126-L5 p. 15; 508583-01 p. 50
E120“Unresponsive device.”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 62; 508589-02 p. 45; 506509-01 p. 65
E124“Active communicating thermostat signal missing for more than 3 minutes.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL297*V, G71MPPTechnician508559-01 p. 28; 508561-01 p. 35; 508585-02 p. 48; 506610-01 p. 62; 508589-02 p. 45; 1126-L5 p. 16; 508583-01 p. 51; 506509-01 p. 65
E125“Control failed self-check, internal error, failed hardware. Will restart if error recovers. Integrated control not communicating. Covers hardware errors (flame sense circuit faults, pin shorts, etc.).”
What to check		SL280*V, SL280*NV, SL297*NV, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*VTechnician508559-01 p. 28; 508561-01 p. 35; 508585-02 p. 48; 1126-L5 p. 16; 1246-L10 p. 13; 508583-01 p. 51; 508577-02 p. 42; 1901-L1 p. 14; 508575-02 p. 46; 508573-01 p. 45; 508545-01 p. 28; 508547-01 p. 48; 508565-01 p. 42; 508569-01 p. 45; 508521-01 p. 41; 508907-01 p. 45
E125“Control failed self-check, internal error, failed hardware. Will restart if error recovers. Integrated furnace control not communicating. Covers hardware errors (flame sense circuit faults, pin shorts, etc.).”
What to check		SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 62; 508589-02 p. 45; 506509-01 p. 65
E126“Control internal communication problem.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician1116-L4 p. 24; 508150-02 p. 46; 1802-L1 p. 17; 1126-L5 p. 16; 100088 p. 39
E126“Failed internal control communication between microcontrollers.”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 62; 508589-02 p. 45; 506509-01 p. 65
E131“Corrupted control parameters (Verify configuration of system). Communicating only.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*V, EL297*ETechnician508559-01 p. 28; 508561-01 p. 35; 508585-02 p. 48; 1126-L5 p. 16; 508583-01 p. 51; 508577-02 p. 42
E131“Corrupted control parameters (Verify configuration of system).”SLP98*V, G71MPPTechnician506610-01 p. 62; 506509-01 p. 65
E150“A2L Refrigerant leak alarm”SL280*V, SL280*NV, SL297*NV, EL297*V, EL297*E, ML296*V, ML297*VTechnician508559-01 p. 28; 508561-01 p. 35; 508585-02 p. 48; 508583-01 p. 51; 508577-02 p. 43; 508521-01 p. 42; 508907-01 p. 46
E150“Refrigerant Leak detected”SLP99*V, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician508589-02 p. 48; 508575-02 p. 46; 508573-01 p. 45; 508545-01 p. 28; 508547-01 p. 48; 508565-01 p. 42; 508569-01 p. 45
E150“A2L Refigerant leak alarm”SL280*V, EL296*V, EL297*VTechnician508246-01 p. 47; 1126-L5 p. 23; 100088 p. 32
E151“Refrigerant Leak Detector Sensor #1 fault”SL280*V, SL280*NV, SL297*NV, SLP99*V, EL297*V, EL297*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*VTechnician508559-01 p. 28; 508561-01 p. 35; 508585-02 p. 48; 508589-02 p. 48; 508583-01 p. 51; 508577-02 p. 43; 508575-02 p. 46; 508573-01 p. 45; 508545-01 p. 28; 508547-01 p. 48; 508565-01 p. 42; 508569-01 p. 45; 508521-01 p. 42; 508907-01 p. 46
E151“A2L Sensor fault (sensor problem) (communication mode only)”SL280*V, EL296*V, EL297*VTechnician508246-01 p. 47; 1126-L5 p. 23; 100088 p. 32
E152“Refrigerant Leak Detector #2 Fault”SL280*V, SL280*NV, SL297*NV, EL297*V, EL297*E, ML296*V, ML297*VTechnician508559-01 p. 28; 508561-01 p. 35; 508585-02 p. 48; 508583-01 p. 51; 508577-02 p. 43; 508521-01 p. 42; 508907-01 p. 46
E152“Refrigerant Leak Detector Sensor #2 fault”SLP99*V, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician508589-02 p. 48; 508575-02 p. 46; 508573-01 p. 45; 508545-01 p. 28; 508547-01 p. 48; 508565-01 p. 42; 508569-01 p. 45
E154“Refrigerant Leak Detector Sensor #1 Communication lost or invalid sensor dip switch configuration (Disable/Enable)”SLP99*V, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician508589-02 p. 48; 508575-02 p. 46; 508573-01 p. 45; 508545-01 p. 28; 508547-01 p. 48; 508565-01 p. 42; 508569-01 p. 45
E154“Refrigerant Leak Detector #1 Communication lost or invalid sensor dip switch configuration (Disable/Enable)”SL280*V, SL280*NV, SL297*NV, EL297*V, EL297*E, ML296*VTechnician508559-01 p. 28; 100175 p. 13; 508585-02 p. 48; 508583-01 p. 51; 508577-02 p. 43; 100179 p. 12
E154“Refrigerant Leak Detector #1 Communication lost or invalid sensor dip switch configuration (Disable/Enable))”ML296*V, ML297*VTechnician508521-01 p. 42; 508907-01 p. 46
E154“Refrigerant Leak Detector Sensor #1 Communication lost or invalid sensor dip switch configuration (ON/OFF)”SLP99*VTechnician508589-01 p. 46
E154“Refrigerant Leak Detector #1 Communication lost or invalid sensor dip switch configuration (ON/OFF)”SL280*NVTechnician508561-01 p. 35
E154“Refrigerant Leak Detector Sensor #1 Communication lost or invalid sensor dip switch configuration (Disable/Enable))”ML180*Technician508541-01 p. 29
E155“Refrigerant Leak Detector #2 Communication lost”SL280*V, SL280*NV, SL297*NV, EL297*V, EL297*E, ML296*V, ML297*VTechnician508559-01 p. 28; 508561-01 p. 35; 508585-02 p. 48; 508583-01 p. 51; 508577-02 p. 43; 508521-01 p. 42; 508907-01 p. 46
E155“Refrigerant Leak Detector Sensor #2 Communication lost”SLP99*V, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician508589-02 p. 48; 508575-02 p. 46; 508573-01 p. 45; 508545-01 p. 28; 508547-01 p. 48; 508565-01 p. 42; 508569-01 p. 45
E160“Refrigerant Leak Detector Sensor #1 type incorrect”SL280*V, SL280*NV, SL297*NV, SLP99*V, EL297*V, EL297*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*VTechnician508559-01 p. 28; 508561-01 p. 35; 508585-02 p. 48; 508589-02 p. 48; 508583-01 p. 51; 508577-02 p. 43; 508575-02 p. 46; 508573-01 p. 45; 508545-01 p. 28; 508547-01 p. 48; 508565-01 p. 42; 508569-01 p. 45; 508521-01 p. 42; 508907-01 p. 46
E161“Refrigerant Leak Detector Sensor #2 type incorrect”SL280*V, SL280*NV, SL297*NV, SLP99*V, EL297*V, EL297*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*VTechnician508559-01 p. 29; 508561-01 p. 36; 508585-02 p. 49; 508589-02 p. 48; 508583-01 p. 52; 508577-02 p. 43; 508575-02 p. 46; 508573-01 p. 45; 508545-01 p. 28; 508547-01 p. 48; 508565-01 p. 42; 508569-01 p. 45; 508521-01 p. 42; 508907-01 p. 46
E163“Furnace Control Board Failure”SL280*V, SL280*NV, SL297*NV, SLP99*V, EL297*V, EL297*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*VTechnician508559-01 p. 29; 508561-01 p. 36; 508585-02 p. 49; 508589-02 p. 48; 508583-01 p. 52; 508577-02 p. 43; 508575-02 p. 46; 508573-01 p. 45; 508545-01 p. 28; 508547-01 p. 48; 508565-01 p. 42; 508569-01 p. 45; 508521-01 p. 42; 508907-01 p. 46
E164“Low GWP Test”SL280*V, SL280*NV, SL297*NV, SLP99*V, EL297*V, EL297*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*VTechnician508559-01 p. 29; 508561-01 p. 36; 508585-02 p. 49; 508589-02 p. 48; 508583-01 p. 52; 508577-02 p. 44; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 48; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 43; 508907-01 p. 47
E180“Outdoor air temperature sensor failure. Only shown if shorted or out-ofrange.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician508246-01 p. 47; 508150-02 p. 46; 1802-L1 p. 17; 1126-L5 p. 23; 100088 p. 32
E180“Outdoor air temperature sensor failure. Only shown if shorted or out-of range.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician508559-01 p. 29; 508561-01 p. 36; 508585-02 p. 49; 1126-L5 p. 16; 508583-01 p. 52
E180“Outdoor air sensor failure - NO error if disconnected. Only shown if shorted or out-of-range.”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 62; 508589-02 p. 45; 506509-01 p. 65
E180“Outdoor air temperature sensor failure. Only shown if shorted or out-of- range.”SL280*VTechnician506763-01 p. 62
E200“Hard lockout - Rollout circuit open or previously open.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 29; 508561-01 p. 36; 508585-02 p. 49; 506610-01 p. 62; 508589-02 p. 45; 1126-L5 p. 16; 1246-L10 p. 13; 508583-01 p. 52; 508577-02 p. 44; 1901-L1 p. 14; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 48; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 43; 508907-01 p. 47; 506509-01 p. 65
E201“Indoor blower communication failure - Unable to communicate with blower motor.”
What to check		SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL297*V, G71MPPTechnician508559-01 p. 29; 508561-01 p. 36; 508585-02 p. 49; 506610-01 p. 62; 508589-02 p. 45; 1126-L5 p. 16; 508583-01 p. 52; 506509-01 p. 65
E202“Indoor blower motor mis-match - Indoor motor horsepower does not match unit capacity.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL297*V, G71MPPTechnician508559-01 p. 29; 508561-01 p. 36; 508585-02 p. 49; 506610-01 p. 62; 508589-02 p. 45; 1126-L5 p. 16; 508583-01 p. 52; 506509-01 p. 65
E203“Appliance capacity / size is NOT programmed. Invalid unit codes refer to configuration flow chart.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician508559-01 p. 29; 508561-01 p. 36; 508585-02 p. 49; 1126-L5 p. 16; 508583-01 p. 52
E203“Appliance capacity / size is NOT programmed. Invalid unit codes refer to configuration flow chart in installation instructions.”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 62; 508589-02 p. 46; 506509-01 p. 65
E204“Gas valve mis-wired.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 29; 508561-01 p. 36; 508585-02 p. 49; 506610-01 p. 62; 508589-02 p. 46; 1126-L5 p. 16; 1246-L10 p. 13; 508583-01 p. 52; 508577-02 p. 44; 1901-L1 p. 14; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 48; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 43; 508907-01 p. 47; 506509-01 p. 65
E205“Gas valve control relay contact shorted.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 29; 508561-01 p. 36; 508585-02 p. 49; 506610-01 p. 62; 508589-02 p. 46; 1126-L5 p. 16; 1246-L10 p. 13; 508583-01 p. 52; 508577-02 p. 44; 1901-L1 p. 14; 508521-01 p. 43; 508907-01 p. 47; 506509-01 p. 65
E206“Gas valve second-stage relay failure”SL280*V, SL280*NV, SL297*NV, EL296*V, EL296*E, EL297*V, EL280*ETechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 1126-L5 p. 17; 1246-L10 p. 13; 508583-01 p. 53; 1901-L1 p. 14
E207“Hot surface ignitor sensed open”
What to check		SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 506610-01 p. 62; 508589-02 p. 46; 1126-L5 p. 17; 1246-L10 p. 13; 508583-01 p. 53; 508577-02 p. 44; 1901-L1 p. 14; 508521-01 p. 43; 508907-01 p. 47; 506509-01 p. 65
E223“Low pressure switch failed open.”
What to check		SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 17; 1246-L10 p. 13; 508583-01 p. 53; 508577-02 p. 44; 1901-L1 p. 14; 508521-01 p. 43; 508907-01 p. 47; 506509-01 p. 66
E223“Pressure switch failed open.”
What to check		EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46
E224“Low pressure switch failed closed”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 17; 1246-L10 p. 13; 508583-01 p. 53; 508577-02 p. 44; 1901-L1 p. 14; 508521-01 p. 43; 508907-01 p. 47; 506509-01 p. 66
E224“Pressure switch failed closed.”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46
E225“High pressure switch failed open.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 17; 1246-L10 p. 13; 508583-01 p. 53; 508577-02 p. 44; 1901-L1 p. 14; 508521-01 p. 43; 508907-01 p. 47; 506509-01 p. 66
E226“High pressure switch failed closed”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 17; 1246-L10 p. 13; 508583-01 p. 53; 508577-02 p. 44; 1901-L1 p. 14; 508521-01 p. 43; 508907-01 p. 47; 506509-01 p. 66
E227“Low pressure switch open during trial for ignition or run mode.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 17; 1246-L10 p. 13; 508583-01 p. 53; 508577-02 p. 44; 1901-L1 p. 14; 508521-01 p. 43; 508907-01 p. 47; 506509-01 p. 66
E227“Pressure switch open during trial for ignition or run mode.”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46
E228“Combustion air inducer calibration failure”
What to check		SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*V, EL297*ETechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 1126-L5 p. 17; 508583-01 p. 53; 508577-02 p. 44
E228“Unable to perform successful pressure switch calibration.”
What to check		SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 63; 508589-02 p. 46; 506509-01 p. 66
E229“Ignition on high fire”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*V, EL297*E, ML296*V, ML297*VTechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 1126-L5 p. 17; 508583-01 p. 53; 508577-02 p. 44; 508521-01 p. 43; 508907-01 p. 47
E229“Ignition on High Fire - Information Only.”EL296*E, EL280*ETechnician1246-L10 p. 13; 1901-L1 p. 14
E240“Low flame current - Run mode.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 17; 1246-L10 p. 13; 508583-01 p. 53; 508577-02 p. 44; 1901-L1 p. 14; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 43; 508907-01 p. 47; 506509-01 p. 66
E241“Flame sensed out of sequence - Flame still present.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 17; 1246-L10 p. 13; 508583-01 p. 53; 508577-02 p. 45; 1901-L1 p. 14; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 44; 508907-01 p. 48; 506509-01 p. 66
E250“Limit switch circuit open.”
What to check		SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 17; 1246-L10 p. 13; 508583-01 p. 53; 508577-02 p. 45; 1901-L1 p. 14; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 44; 508907-01 p. 48; 506509-01 p. 66
E252“Discharge air temperature too high (gas heat only).”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL297*V, G71MPPTechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 17; 508583-01 p. 53; 506509-01 p. 66
E270“Soft lockout - Exceeded maximum number of retries. No flame current sensed.”
What to check		SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 30; 508561-01 p. 37; 508585-02 p. 50; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 17; 1246-L10 p. 14; 508583-01 p. 53; 508577-02 p. 45; 1901-L1 p. 15; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 44; 508907-01 p. 48; 506509-01 p. 66
E271“Soft lockout - Exceeded maximum number of retries. Last retry failed due to the pressure switch opening.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 31; 508561-01 p. 38; 508585-02 p. 51; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 18; 1246-L10 p. 14; 508583-01 p. 54; 508577-02 p. 45; 1901-L1 p. 15; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 44; 508907-01 p. 48; 506509-01 p. 66
E272“Soft lockout - Exceeded maximum number of recycles. Last recycle due to the pressure switch opening.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 31; 508561-01 p. 38; 508585-02 p. 51; 506610-01 p. 63; 508589-02 p. 46; 1126-L5 p. 18; 1246-L10 p. 14; 508583-01 p. 54; 508577-02 p. 45; 1901-L1 p. 15; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 44; 508907-01 p. 48; 506509-01 p. 66
E273“Soft lockout - Exceeded maximum number of recycles. Last recycle due to flame failure.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 31; 508561-01 p. 38; 508585-02 p. 51; 506610-01 p. 63; 508589-02 p. 47; 1126-L5 p. 18; 1246-L10 p. 14; 508583-01 p. 54; 508577-02 p. 45; 1901-L1 p. 15; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 44; 508907-01 p. 48; 506509-01 p. 66
E274“Soft lockout - Exceeded maximum number of recycles. Last recycle failed due to the limit circuit opening or limit remained open longer than 3 minutes”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*V, G71MPPTechnician508559-01 p. 31; 508561-01 p. 38; 508585-02 p. 51; 506610-01 p. 63; 508589-02 p. 47; 1126-L5 p. 18; 1246-L10 p. 14; 508583-01 p. 54; 508577-02 p. 45; 1901-L1 p. 15; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 44; 508907-01 p. 48; 506509-01 p. 66
E275“Soft lockout - Flame sensed out of sequence. Flame signal is gone.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*VTechnician508559-01 p. 31; 508561-01 p. 38; 508585-02 p. 51; 1126-L5 p. 18; 1246-L10 p. 14; 508583-01 p. 54; 508577-02 p. 45; 1901-L1 p. 15; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 44; 508907-01 p. 48
E275“Soft lockout - Flame sensed out of sequence from code 241 fault. Flame signal is gone.”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 63; 508589-02 p. 47; 506509-01 p. 66
E276“Watchguard calibration failure.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician1116-L4 p. 26; 508150-02 p. 48; 1802-L1 p. 19; 1126-L5 p. 18; 100088 p. 41
E276“Soft lockout - Exceeded maximum number of calibration retries.”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 63; 508589-02 p. 47; 506509-01 p. 66
E290“Ignitor circuit fault - Failed ignitor or triggering circuitry.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL296*E, EL297*V, EL297*E, EL280*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, G71MPPTechnician508559-01 p. 31; 508561-01 p. 38; 508585-02 p. 51; 506610-01 p. 63; 508589-02 p. 47; 1126-L5 p. 18; 1246-L10 p. 14; 508583-01 p. 54; 508577-02 p. 45; 1901-L1 p. 15; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46; 506509-01 p. 66
E291“Heat air flow restricted below the minimum.”
What to check		SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician1116-L4 p. 26; 508150-02 p. 48; 1802-L1 p. 19; 1126-L5 p. 18; 100088 p. 41
E291“Restricted air flow - Cubic feet per minute is lower than what is needed for minimum firing rate.”
What to check		SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 63; 508589-02 p. 47; 506509-01 p. 66
E292“Indoor blower motor unable to start due to obstructed wheel, seized bearings.”
What to check		SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*V, ML180*, ML296*V, ML297*VTechnician508559-01 p. 31; 508561-01 p. 38; 508585-02 p. 51; 1126-L5 p. 18; 508583-01 p. 54; 508547-01 p. 49; 508521-01 p. 44; 508907-01 p. 48
E292“Indoor blower motor unable to start - Seized bearings, stuck wheel, etc.”
What to check		SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 63; 508589-02 p. 47; 506509-01 p. 66
E294“Combustion air inducer over current.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician1116-L4 p. 26; 508150-02 p. 48; 1802-L1 p. 19; 1126-L5 p. 18; 100088 p. 41
E294“Combustion air inducer motor amp draw is too high.”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 63; 508589-02 p. 47; 506509-01 p. 66
E295“Indoor blower motor temperature is too high.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL297*V, G71MPPTechnician508559-01 p. 31; 508561-01 p. 38; 508585-02 p. 51; 506610-01 p. 64; 508589-02 p. 47; 1126-L5 p. 18; 508583-01 p. 54; 506509-01 p. 67
E310“Discharge error temperature sensor failure. Only shown if shorted or out of range.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician508559-01 p. 31; 508561-01 p. 38; 508585-02 p. 51; 1126-L5 p. 18; 508583-01 p. 54
E310“Discharge error sensor failure - No error if disconnected. Only shown if shorted or out-of-range.”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 64; 508589-02 p. 47; 506509-01 p. 67
E311“Heat rate reduced to match indoor blower air flow.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*V, ML296*V, ML297*VTechnician508559-01 p. 31; 508561-01 p. 38; 508585-02 p. 51; 1126-L5 p. 18; 508583-01 p. 54; 508521-01 p. 44; 508907-01 p. 48
E311“Heat rate reduced to match indoor blower air flow. Replace filter or repair duct restriction.”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 64; 508589-02 p. 47; 506509-01 p. 67
E312“Restricted air flow in cooling or continuous fan mode is lower than cfm setting.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL297*V, G71MPPTechnician508559-01 p. 32; 508561-01 p. 39; 508585-02 p. 52; 506610-01 p. 64; 508589-02 p. 47; 1126-L5 p. 19; 508583-01 p. 55; 506509-01 p. 67
E313“Indoor or outdoor unit capacity mismatch. Communication only.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician508559-01 p. 32; 508561-01 p. 39; 508585-02 p. 52; 1126-L5 p. 19; 508583-01 p. 55
E313“Indoor or outdoor unit capacity mismatch.”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 64; 508589-02 p. 47; 506509-01 p. 67
E331“Global network connection - Communication link problem.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL297*V, G71MPPTechnician508245-01 p. 56; 508150-02 p. 49; 1802-L1 p. 20; 506610-01 p. 64; 508589-02 p. 47; 1126-L5 p. 19; 100088 p. 42; 506509-01 p. 67
E334“Relay "Y1" stuck on interated control.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician508559-01 p. 32; 508561-01 p. 39; 508585-02 p. 52; 1126-L5 p. 26; 508583-01 p. 55
E334“Relay "Y1" stuck on integrated control.”EL296*V, EL297*VTechnician1126-L5 p. 19; 100088 p. 42
E344“Relay "Y1" stuck on interated control.”SL297*NVTechnician1802-L1 p. 20
E345“Relay O Failure”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician508559-01 p. 32; 508561-01 p. 39; 508585-02 p. 52; 1126-L5 p. 26; 508583-01 p. 55
E345“O Relay Failure”SLP99*VTechnician508589-02 p. 47
E347“No 24 Volt output on Y1 of "integrated control" with non communicating outdoor unit.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician508559-01 p. 32; 508561-01 p. 39; 508585-02 p. 52; 1126-L5 p. 19; 508583-01 p. 55
E347“No 24 Volt output on Y1 to C with non-communicating outdoor unit.”SLP98*V, G71MPPTechnician506610-01 p. 64; 506509-01 p. 67
E347“No 24 Volt output on Y1 to C with noncommunicating outdoor unit.”SLP99*VTechnician508589-02 p. 47
E348“No 24 Volt output on Y2 of "integrated control" with non?communicating outdoor unit.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician508559-01 p. 32; 508561-01 p. 39; 508585-02 p. 52; 1126-L5 p. 19; 508583-01 p. 55
E348“No 24 Volt output on Y2 to C with non-communicating outdoor unit.”SLP98*V, G71MPPTechnician506610-01 p. 64; 506509-01 p. 67
E348“No 24 Volt output on Y2 to C with noncommunicating outdoor unit.”SLP99*VTechnician508589-02 p. 47
E349“No 24 Volts between R & O on "integrated control" with non communicating outdoor unit (Dual fuel module required for heat pump application”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician1116-L4 p. 27; 508150-02 p. 49; 1802-L1 p. 20; 1126-L5 p. 19; 100088 p. 42
E349“No 24 Volts between R & O with non-communicating outdoor unit (Dual fuel module required for heat pump application).”SLP98*V, G71MPPTechnician506610-01 p. 64; 506509-01 p. 67
E349“No 24 Volts between R & O with noncommunicating outdoor unit (Dual fuel module required for heat pump application).”SLP99*VTechnician508589-01 p. 45
E349“No 24 Volts between R & O on "integrated control" with non communicating outdoor unit (Dual fuel module required for heat pump application).”SL280*VTechnician506763-01 p. 65
E370“Interlock switch sensed open for 2 minutes.”SL280*V, SL280*NV, SL297*NV, SLP99*V, EL296*V, EL297*VTechnician508559-01 p. 32; 508561-01 p. 39; 508585-02 p. 52; 508589-02 p. 47; 1126-L5 p. 19; 508583-01 p. 55
E390“Low GWP Relay Stuck”SL280*V, SL280*NV, SL297*NV, SLP99*V, EL297*V, EL297*E, EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*E, ML296*V, ML297*VTechnician508559-01 p. 32; 508561-01 p. 39; 508585-02 p. 52; 508589-02 p. 48; 508583-01 p. 55; 508577-02 p. 45; 508575-02 p. 47; 508573-01 p. 46; 508545-01 p. 29; 508547-01 p. 49; 508565-01 p. 43; 508569-01 p. 46; 508521-01 p. 44; 508907-01 p. 48
E400“LSOM - Compressor internal overload tripped.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician1116-L4 p. 27; 508150-02 p. 49; 1802-L1 p. 20; 1126-L5 p. 19; 100088 p. 42
E401“LSOM Compressor long run cycle or low system pressure.”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician1116-L4 p. 27; 508150-02 p. 49; 1802-L1 p. 20; 1126-L5 p. 19; 100088 p. 42
E401“LSOM - Compressor ran more than 18 hours in air conditioning mode.”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 64; 507999-02 p. 62; 506509-01 p. 67
E402“LSOM - Outdoor unit system pressure trip.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL297*V, G71MPPTechnician1116-L4 p. 27; 508150-02 p. 49; 1802-L1 p. 20; 506610-01 p. 64; 507999-02 p. 63; 1126-L5 p. 19; 100088 p. 42; 506509-01 p. 67
E403“LSOM - Compressor short-cycling. .(Running less than 4 minutes). Outdoor unit pressure trip”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician1116-L4 p. 27; 508150-02 p. 49; 1802-L1 p. 20; 1126-L5 p. 19; 100088 p. 42
E403“LSOM - Compressor short-cycling (Running less than 4 minutes).”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 64; 507999-02 p. 63; 506509-01 p. 67
E404“LSOM - Compressor rotor locked. Compressor short-cycling. (Running less than 4 minutes).”SL280*V, SL280*NV, SL297*NV, EL296*V, EL297*VTechnician1116-L4 p. 27; 508150-02 p. 49; 1802-L1 p. 20; 1126-L5 p. 19; 100088 p. 42
E404“LSOM - Compressor rotor locked.”SLP98*V, SLP99*V, G71MPPTechnician506610-01 p. 64; 507999-02 p. 63; 506509-01 p. 67
E405“LSOM - Compressor open circuit.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL297*V, G71MPPTechnician1116-L4 p. 27; 508150-02 p. 49; 1802-L1 p. 20; 506610-01 p. 64; 507999-02 p. 63; 1126-L5 p. 19; 100088 p. 42; 506509-01 p. 67
E406“LSOM - Compressor open start circuit.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL297*V, G71MPPTechnician1116-L4 p. 28; 508150-02 p. 50; 1802-L1 p. 21; 506610-01 p. 64; 507999-02 p. 63; 1126-L5 p. 20; 100088 p. 43; 506509-01 p. 67
E407“LSOM - Compressor open run circuit.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL297*V, G71MPPTechnician1116-L4 p. 28; 508150-02 p. 50; 1802-L1 p. 21; 506610-01 p. 64; 507999-02 p. 63; 1126-L5 p. 20; 100088 p. 43; 506509-01 p. 67
E408“LSOM - Compressor contactor is welded.”SL280*V, SL280*NV, SL297*NV, SLP98*V, SLP99*V, EL296*V, EL297*V, G71MPPTechnician1116-L4 p. 28; 508150-02 p. 50; 1802-L1 p. 21; 506610-01 p. 64; 507999-02 p. 63; 1126-L5 p. 20; 100088 p. 43; 506509-01 p. 67
E409“LSOM - Compressor low voltage.”SL280*V, SL280*NV, SL297*NV, SLP98*V, EL296*V, EL297*V, G71MPPTechnician1116-L4 p. 28; 508150-02 p. 50; 1802-L1 p. 21; 506610-01 p. 64; 1126-L5 p. 20; 100088 p. 43; 506509-01 p. 67
E409“LSOM - Compressor contactor is welded.”SLP99*VTechnician507999-02 p. 63
1 flash“Reverse Line Voltage Polarity”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
1 flash“Reverse Line Voltage Polarity or Phasing of 120V power”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 44; 507764-06 p. 41; 507647-05 p. 25; 507103-04 p. 27; 507863-02 p. 40; 507966-04 p. 41
1 flash“Flame present with gas vavle de-energized.”ML180*, ML193*E, ML195*, ML296*VTechnician507326-01 p. 21; 507121-01 p. 39; 507268-03 p. 39; 507869-04 p. 46
2 flashes“Improper Earth Ground”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
2 flashes“Pressure switch closed with combustion air inducer de-energized.”ML180*, ML193*E, ML296*VTechnician507326-01 p. 21; 507121-01 p. 39; 507869-04 p. 46
2 flashes“Pressure switch closed with combustion air inducer e-energized.”ML195*Technician507268-03 p. 39
3 flashes“Burner failed to light, or lost flame during heat demand”
What to check		EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
3 flashes“Pressure switch open with combustion air inducer energized.”
What to check		ML180*, ML193*E, ML195*Technician507326-01 p. 21; 507121-01 p. 39; 507268-03 p. 39
3 flashes“Pressure switch open with inducer energized”
What to check		ML296*VTechnician507869-04 p. 46
3 flashes“Low-fire pressure, rollout or limit switch open.”
What to check		ML296*VTechnician1904-L1 p. 8
4 flashes“Low Flame Signal - check flame sensor”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
4 flashes“Low flame signal – check flame sensor”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 44; 507764-06 p. 41; 507647-05 p. 25; 507103-04 p. 27; 507863-02 p. 40; 507966-04 p. 41
4 flashes“Primary limit switch open.”ML180*, ML193*E, ML195*, ML296*VTechnician507326-01 p. 21; 507121-01 p. 39; 507268-03 p. 39; 1904-L1 p. 8
4 flashes“Primary limit, secondarylLimit, or roll-out switch open”ML296*VTechnician507869-04 p. 46
5 flashes“Watchguard - burner failed to light, exceeded maximum number of retries or recycles.”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
5 flashes“Watchguard – burner failed to light, exceeded maximum number of retries/recycles, 1 hour lockout”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 44; 507764-06 p. 41; 507647-05 p. 25; 507103-04 p. 27; 507863-02 p. 40; 507966-04 p. 41
5 flashes“Rollout switch open.”ML180*, ML193*E, ML195*Technician507326-01 p. 21; 507121-01 p. 39; 507268-03 p. 39
6 flashes“Pressure switch cycle lockout.”ML180*, ML193*E, ML195*, ML296*VTechnician507326-01 p. 21; 507121-01 p. 39; 507268-03 p. 39; 507869-04 p. 46
6 flashes“Ignitor Circuit Failure - not available on this control”EL195*NE, ML180*Technician506596-01 p. 49; 1121-L4 p. 8
7 flashes“Primary or Secondary Limit Open or Watchguard Mode - Limit Switch Open longer than 3 minutes”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
7 flashes“Primary or Secondary limit switch open or Watchguard mode – Limit Switch open longer than 3 minutes”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 44; 507764-06 p. 41; 507647-05 p. 25; 507103-04 p. 27; 507863-02 p. 40; 507966-04 p. 41
7 flashes“Lockout, burners fail to light.”ML180*, ML193*E, ML195*, ML296*VTechnician507326-01 p. 21; 507121-01 p. 39; 507268-03 p. 39; 507869-04 p. 46
8 flashes“Rollout Switch Open”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
8 flashes“Roll-out Switch Open”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 44; 507764-06 p. 41; 507647-05 p. 25; 507103-04 p. 27; 507863-02 p. 40; 507966-04 p. 41
8 flashes“Lockout, buners lost flame too many times.”ML180*, ML193*E, ML195*, ML296*VTechnician507326-01 p. 21; 507121-01 p. 39; 507268-03 p. 39; 1904-L1 p. 8
8 flashes“Lockout, burners lost flame too many times.”ML296*VTechnician507869-04 p. 46
9 flashes“Pressure Switch failed to close or opened during heat demand”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
9 flashes“Pressure Switch failed to close or opened during heat demand, inducer on”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 44; 507764-06 p. 41; 507647-05 p. 25; 507103-04 p. 27; 507863-02 p. 40; 507966-04 p. 41
9 flashes“Line voltage polarity incorrect.”ML180*, ML193*E, ML195*, ML296*VTechnician507326-01 p. 21; 507121-01 p. 39; 507268-03 p. 39; 507869-04 p. 46
10 flashes“Watchguard - Pressure Switch opened 5 times during one heat demand”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
10 flashes“Watchguard - Pressure switch opened 5 times during a single heating demand”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 44; 507764-06 p. 41; 507647-05 p. 25; 507103-04 p. 27; 507863-02 p. 40; 507966-04 p. 41
11 flashes“Pressure Switch stuck closed prior to activation of combustion air inducer”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
12 flashes“Flame Sensed without gas valve energized”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
13 flashes“Low Line Voltage”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
Green LED flashing“High heat demand, high pressure switch not closed”ML296*VTechnician507869-04 p. 46
Green LED off“No demand for high heat”ML296*VOwner can check507869-04 p. 46
Green LED on“High heat demand, operating normally”ML296*VOwner can check507869-04 p. 46
LED off“No power to control or board fault detected”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
LED off“No power to control or control harware fault detected.”ML180*, ML193*E, ML195*, ML296*VTechnician507326-01 p. 21; 507121-01 p. 39; 507268-03 p. 39; 1904-L1 p. 8
LED off“No power to control or control hardware fault detected.”ML296*VTechnician507869-04 p. 46
LED off“Normal operation.”ML180*Owner can check507326-01 p. 21
LED on“Board Fault Detected”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*ETechnician507758-05 p. 44; 507764-06 p. 41; 507647-05 p. 25; 507945-02 p. 26; 507863-02 p. 40; 507966-04 p. 41
LED on“Normal operation.”ML193*E, ML195*, ML296*VOwner can check507121-01 p. 39; 507268-03 p. 39; 507869-04 p. 46
continuous rapid flash“Call For Heat / Burner Operation”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*EOwner can check507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
fast heartbeat“Call for Heat / Burner Operation”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*EOwner can check507758-05 p. 44; 507764-06 p. 41; 507647-05 p. 25; 507103-04 p. 27; 507863-02 p. 40; 507966-04 p. 41
heartbeat“Normal Operation - Idle, Continuous Fan, Cool”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*EOwner can check507758-05 p. 43; 507764-06 p. 40; 507647-05 p. 24; 507945-02 p. 26; 507863-02 p. 39; 507966-04 p. 40
heartbeat“Control powered - displayed during all modes of operation if no errors are detected”EL195*NEOwner can check506596-01 p. 49
slow heartbeat“Normal Operation – Idle, Continuous Fan, or Cool”EL195*NE, EL196*E, EL180*NE, ML180*, ML193*E, ML196*EOwner can check507758-05 p. 44; 507764-06 p. 41; 507647-05 p. 25; 507103-04 p. 27; 507863-02 p. 40; 507966-04 p. 41

How to read a Lennox furnace code

These pages cover Lennox gas furnaces. How a fault is shown depends on the furnace’s control board. Lennox prints its code tables in the installation instructions and in its Unit Information service literature; none of the Lennox owner’s manuals used for these pages has a code table.

Seven-segment display: E-codes and modes

Furnaces whose tables use E-codes have a seven-segment display on the integrated control. The SL297UHNVK installation instructions say it shows operating status, target airflow, error codes and other information 508585-02, p. 46. An error code is an E and three digits, such as E201 or E228, and E000 means no error in memory. Letters and symbols shown on their own are operating modes, not faults: a decimal point blinking once a second is idle, C is a cooling stage, H a gas heat stage (blinking during ignition), h a heat pump stage, d dehumidification, dF defrost, A the blower airflow setting and U the discharge air temperature 508585-02, p. 47.

The SL297UHNVK control keeps the 10 most recent error codes. Recalling and clearing them is done with the diagnostic push button next to the display, in a procedure the installation instructions write for the installer 508585-02, p. 46; these pages do not repeat it.

The SLP99DFVK owner’s manual does not mention the display. The SL280UHNV and SL297UHNV owner’s manuals do: when the furnace begins heating, the diagnostic LED on the furnace control displays “H1” for heating in the first stage or “H2” for heating in the second stage, and it can be seen through the viewport on the lower access panel 507650-01, p. 3; 507761-01, p. 4.

Red LED: heartbeat and flash counts

Furnaces whose tables use flash counts report faults with a red LED on the control. The EL180UHNE and EL195UHNE owner’s manuals describe its normal states: a “slow flash”, 1 second on and 1 second off, when the furnace is not in operation, and a “continuous rapid flash” on a call for heat and during normal heating. They say the red LED can be seen through the viewport on the lower access panel 507648-02, p. 3; 507759-01, p. 4.

A fault code is a count. The notes under the tables for the 103217-03 and 107163-01 boards say the LED flashes X times at ½ second on and ½ second off, stays off for 3 seconds, then repeats 1911-L7, p. 10; 507966-04, p. 41. On the 107163-01 board the “fast heartbeat” of a heat call is also 0.5 second on and 0.5 second off 507966-04, p. 41; in the notes, the difference is the 3-second pause that follows a code. The ML180UHV table gives 1/3 second on and 1/3 second off for code flashes 507945-02, p. 26.

A steady light means different things on different boards. In the 13-flash tables, off means no power to the control or a board fault, and on the 107163-01 board a steady light means “Board Fault Detected” 507966-04, pp. 40–41. In older 9-flash tables “LED On” is normal operation 507121-01, p. 39; 507869-04, p. 46, and the 2018 ML180DF table lists “LED Off” twice, once for no power or a control hardware fault and once for normal operation 507326-01, p. 21.

ML296: green and amber LEDs

The ML296UHV control adds a green LED for the high heat state: off is no demand for high heat, on is high heat demand with normal operation, and flashing is “High heat demand, high pressure switch not closed”. An amber LED shows blower airflow, and each of its flashes stands for 100 CFM 507869-04, p. 46.

Two 2011 layouts are not in the table on this page: an ML180UH board with a red and a green LED whose code is a combination of the two 506816-01, p. 39, and a G61MPV board whose red LED flashes two numbers, X + Y, with a pause between them 506506-01, p. 63.

Thermostat alert numbers

On a Lennox communicating system the thermostat shows alerts with a number, a text and a priority. Lennox’s Alert Code Guide and its S30 and E30 thermostat guides print the alert tables 100017, pp. 8–51; 507536-08, 3/2025, pp. 58–102; 507686-06, 03/2023, pp. 36–46. For example, alert 228 is “GF Inducer Calibration Issue”, priority Service Soon 100017, p. 21. The S30 guide says Service Urgent alerts appear on the Home screen under the homeowner and installer alert buttons, Service Soon alerts only under the installer alert button, and “Information Only are not reported to homeowner or dealer.” 507536-08, 3/2025, p. 56.

Many alert numbers are the same as display codes. The Lennox documents do not say that an alert and a display code with the same number report the same event, and the words differ: alert 250 is “GF Primary Limit Switch Open” 100017, p. 22, display code E250 is “Limit switch circuit open.” 508585-02, p. 50. The table on this page lists the furnace’s own codes; each code page names the alert with the same number where there is one.

Codes such as c2, a760 or 3228 show up in search suggestions (Google autocomplete, checked October 20, 2026), but they are not printed as codes in the Lennox documents used for these pages.

Why a flash count needs the board

The same count has different meanings in different Lennox tables. Five columns, quoted as printed (13-flash table: 507966-04, p. 40; 9-flash tables: 507121-01, p. 39, 507268-03, p. 39 and 507326-01, p. 21; ML296UHV: 507869-04, p. 46; ML296DFV(X): 1904-L1, p. 8):

Flashes 13-flash table, board 103217-03 9-flash tables: ML193UH, ML195UH, ML180DF ML296UHV installation instructions ML296DFV(X) service literature
1 “Reverse Line Voltage Polarity” “Flame present with gas vavle de-energized.” same as 9-flash same as 9-flash
3 “Burner failed to light, or lost flame during heat demand” “Pressure switch open with combustion air inducer energized.” “Pressure switch open with inducer energized” “Low-fire pressure, rollout or limit switch open.”
4 “Low Flame Signal - check flame sensor” “Primary limit switch open.” “Primary limit, secondarylLimit, or roll-out switch open” “Primary limit switch open.”
5 “Watchguard - burner failed to light, exceeded maximum number of retries or recycles.” “Rollout switch open.” “Not used” “Not used”
7 “Primary or Secondary Limit Open or Watchguard Mode - Limit Switch Open longer than 3 minutes” “Lockout, burners fail to light.” same as 9-flash same as 9-flash
9 “Pressure Switch failed to close or opened during heat demand” “Line voltage polarity incorrect.” same as 9-flash same as 9-flash

The 103217-02 table has the same wording in these rows 1121-L4, p. 8. The 107163-01 table words some of them differently; for example, its 1 flash adds “or Phasing of 120V power” 507966-04, p. 41. The tables name the board, and several documents print tables for two boards, but none of them says which board a given model or serial number has 507966-04, pp. 40–41; 1121-L4, pp. 8–10.

One series can have both kinds of table in different documents. Within the ML180 series, the 2018 ML180DF instructions have a 9-flash table 507326-01, p. 21, while the 2024 ML180UHV and ML180UHE instructions have 13-flash tables 507945-02, p. 26; 507103-04, pp. 26–27. The ML193 changed the same way between the 2013 ML193UH and the 2024 ML193UHE instructions 507121-01, p. 39; 507863-02, pp. 39–40. For the ML296, the installation instructions and the service literature disagree on 3 and 4 flashes 507869-04, p. 46; 1904-L1, p. 8.

Finding the rows for your furnace

  1. Find the model number. The SLP99DFVK owner’s manual says the model and serial numbers are on the unit nameplate, on the blower deck below the combustion air inducer, and asks you to record them 508590-01, p. 5. Its parts list gives a full model number as an example, SLP99DF070V36BK 508590-01, p. 7. The nameplate location here is from that manual; the owner’s manual for your series gives its own. If reading the nameplate means removing a panel, the same manual says to turn the electrical power to the unit OFF at the disconnect switch before attempting any service or maintenance 508590-01, p. 2 and to disconnect all remote electric power supplies before opening an access panel; the unit may have multiple power supplies 508590-01, p. 5. It also warns that the blower door must be securely in place when the blower and burners are operating 508590-01, p. 3.
  2. Match the start of the model number to a series in the table. The series names come from the covers of Lennox’s installation instructions and service literature. An asterisk stands for the letters that differ between models: SL280*V covers, for example, the SL280UHV, the SL280DFV and the SL280DFVK 508245-01, p. 1; 508246-01, p. 1; 508559-01, p. 1.
  3. Use the edition that matches your furnace. For several series, Lennox’s K editions have E-code tables where the earlier editions have flash tables: the ML196UHE instructions print red LED flash codes 507966-04, pp. 40–41, the ML196UHEK instructions print E-codes 508569-01, pp. 44–46. The ML296DFV(X) and the ML296DFVK differ the same way 1904-L1, p. 8; 508521-01, pp. 41–44. The SLP99DFVK installation instructions list that series’ models, and each of them ends in K, for example SLP99DF070V36BK and SLP99DF090V60CK 508589-02, p. 2. Each row of the table names its document and page, and the document list on this page gives each revision date.
  4. If your series is not in the table, these pages cannot tell you what your code means. They are based on Lennox documents only. Armstrong Air, AirEase and Ducane furnaces have their own model names and literature, which these pages do not use.

Owner checks before a service call

Lennox’s owner’s manuals have no code table and no reset procedure. The SLP99DFVK manual opens its Maintenance section by saying that the maintenance procedures should only be conducted by a licensed professional service technician, and not to attempt to service the unit in any way 508590-01, p. 5. What it gives the owner, further down the same page, is a “Service Reminder”: call your Lennox service technician if the unit will not operate, and before calling, check these items, in this order 508590-01, p. 5:

  1. Check that the electrical disconnect switches are ON 508590-01, p. 5.
  2. Check the room thermostat for proper setting 508590-01, p. 5.
  3. Replace any blown fuses or reset circuit breakers 508590-01, p. 5.
  4. Check that the gas valve is ON 508590-01, p. 5. On the SLP99DFVK the gas valve switch is behind the outer access panel. The manual’s gas valve steps set the thermostat to its lowest setting and turn off all electrical power to the unit before that panel comes off. Move the switch by hand only, never with tools; if it will not move by hand, do not try to repair it, and call a licensed professional service technician 508590-01, p. 4.
  5. Check that the air filter is not plugged, which would limit air flow 508590-01, p. 5. The SLP99DFVK manual says its filters are installed external to the unit, should be inspected monthly, and that a filter must be in place when the unit is operating 508590-01, p. 4. Before any service or maintenance, it says to turn the electrical power to the unit OFF at the disconnect switch 508590-01, p. 2.
  6. Check that gas is turned on at the meter 508590-01, p. 5.
  7. Check that the manual main shut-off valve is open 508590-01, p. 5.

The manual then asks you to record the model and serial number 508590-01, p. 5. The other Lennox owner’s manuals used for these pages print the same seven checks; in the EL180UHNE manual they run over two pages 507648-02, pp. 5–6. The list is for a furnace that will not operate. It is the same whatever code is showing, and the manual does not present it as a way to clear a code.

Shutting off gas to the SLP99DFVK

The steps below are from the SLP99DFVK owner’s manual 508590-01, p. 4. Other Lennox owner’s manuals word them differently; the EL180UHNE manual, for example, says “Remove the upper access panel” and “Move switch on gas valve OFF” 507648-02, p. 4. Use the manual for your own furnace.

The section “Turning Off Gas to the Unit” opens with a warning: if overheating occurs or the gas supply fails to shut off, shut off the manual gas valve to the furnace before shutting off the electrical supply 508590-01, p. 4. Its steps:

  1. Set the thermostat to the lowest setting.
  2. Turn off all electrical power to the unit. In “Operating the Gas Valve” this step is printed without a condition, “Turn off all electrical power to the unit.”; in “Turning Off Gas to the Unit” it reads “Turn off all electrical power to the unit if service is to be performed.” 508590-01, p. 4.
  3. Remove the outer access panel.
  4. Move the gas valve switch to the OFF position.
  5. Replace the outer access panel.

Move the switch by hand only, never with tools; if it will not move by hand, do not try to repair it, and call a licensed professional service technician 508590-01, p. 4. The manual’s start-up steps send you to “Turning Off Gas to the Unit” when the appliance will not operate, and then to your service technician or gas supplier 508590-01, p. 4.

Clearing a code and lockouts

The owner’s manuals give no reset step. The installation instructions describe how the control resets itself, for the installer. On the SL297UHNVK, an internal Watchguard control is an automatic reset for an ignition control lockout caused by ignition failure: after one hour of continuous thermostat demand for heat, it breaks and remakes the demand and resets the control to begin the ignition sequence 508585-02, p. 64. The sequence-of-operation chart in the same document notes “WATCHGUARD LOCKOUT AUTOMATICALLY RESETS AFTER ONE HOUR” and “HARD LOCKOUT REQUIRES THERMOSTAT RESET OR CYCLING OF POWER TO RESET THE LOCKOUT.” 508585-02, p. 69.

The code tables say which codes lock out. In the SL297UHNVK table, E200 is a hard lockout, E270 to E275 are soft lockouts, and E290, E292 and E250 (when the limit does not close within 3 minutes) lead to a 1-hour soft lockout 508585-02, pp. 49–51. The compact ML180UHVK table groups its codes under headings such as “HARD LOCKOUT FAULT”, “SOFT LOCKOUT FAULTS (60 MINUTES)”, “HARDWARE FAULT (5 MINUTES LOCKOUT)” and “ELECTRICAL FAULTS (WAIT FOR RECOVERY)” 508547-01, pp. 26–27. Tables for other series do not always give the same timing, so each code page quotes its own tables.

The owner’s manuals give no step for a code that comes back. These pages treat a code that keeps returning after it clears as a reason to call a technician. The manual’s own instruction covers a unit that will not operate: call your Lennox service technician 508590-01, p. 5.

When to stop and call a professional

The SLP99DFVK owner’s manual says installation and service must be performed by a licensed professional HVAC installer or equivalent, service agency, or the gas supplier 508590-01, p. 1. For your safety and to fulfill the terms of the limited warranty, a licensed professional service technician must inspect the furnace and its vent system every year 508590-01, p. 3. Stop and call when:

  • You smell gas. The steps at the top of every code page are from the cover of the EL180UHNE owner’s manual and include “Leave the building immediately” 507648-02, p. 1. The block on the cover of the SLP99DFVK manual does not have that line 508590-01, p. 1. For LP/propane, the SLP99DFVK manual says the odorant can lose its scent and that an LP/propane leak detector should be installed in all LP applications 508590-01, p. 3.
  • The furnace overheats or the gas supply does not shut off. Shut off the manual gas valve to the furnace before the electrical supply 508590-01, p. 4.
  • Any part of the furnace has been underwater. Do not use it; call a licensed professional service technician to inspect it and replace the gas controls, control system parts and electrical parts that have been wet 508590-01, p. 6.
  • You notice any sign from the manual’s “Safety Precautions”: repeated new or unfamiliar sounds while the unit runs; unusual odors; unusual amounts of condensate on windows, visibly burnt components, or unusual dirt or rust on the vent pipe or in the unit; headache, nausea, fatigue or dizziness, which can be caused by carbon monoxide; the indoor blower running continuously at the cooling speed with no call for cooling, which can mean a refrigerant leak. The manual says to shut down the unit and contact a Lennox dealer for an inspection by a licensed professional service technician 508590-01, p. 6.
  • The gas valve switch will not move by hand 508590-01, p. 4.
  • The furnace still will not operate after the owner checks 508590-01, p. 5.
  • A code keeps coming back after it clears. This is the advice of these pages; the owner’s manuals give no step for error codes.

Carbon monoxide: the manual’s warning is at the top of every code page 508590-01, p. 3. Lennox recommends a carbon monoxide detector in your home, even if you do not own gas appliances, and the SLP99DFVK manual’s carbon monoxide warning asks you to check that the furnace vent and air intake terminals are not obstructed in any way during all seasons 508590-01, p. 3.

See also

Other gas furnaces: Carrier, Goodman, Rheem and Ruud

Lennox is a trademark of its owner. How House Works is not affiliated with or endorsed by Lennox.

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