All Error Codes
High Medium Low
| Code | Description | Severity | Quick Action |
|---|---|---|---|
| E773 | Improper Gas Type Detected | High | Check gas supply |
| E001 | Ignition Failure | Medium | Call tech support |
| E003 | Abnormal Ignition | Medium | Call tech support |
| E004 | False Flame Detection | Medium | Check gas & reset |
| E012 | Flame Loss | Medium | Check gas & reset |
| E016 | Overheating | Medium | Call tech support |
| E030 | Exhaust Overheat Sensor | Medium | Check venting |
| E031 | Inlet Thermistor Open/Short | Medium | Call tech support |
| E046 | Outlet Thermistor Open/Short | Medium | Call tech support |
| E047 | DHW Thermistor Open/Short | Medium | Call tech support |
| E060 | Fan Motor Abnormality | Medium | Clean air filter |
| E109 | Fan Motor Speed Low | Medium | Clean air filter |
| E110 | Exhaust Blocked | Medium | Check venting |
| E205 | Water Flow Sensor Failure | Medium | Call tech support |
| E218 | Bypass Servo Motor Failure | Medium | Call tech support |
| E238 | Abnormal recirculation pump operation ● The pump is turned ON. ● Water flow is N | Medium | Call tech support |
| E278 | Mixing Valve Stuck | Medium | Call tech support |
| E279 | Mixing Valve Open Failure | Medium | Call tech support |
| E291 | Cascade Communication Error | Medium | Check wiring |
| E302 | Remote Controller Communication | Medium | Check wiring |
| E311 | Abnormal water level | Medium | Call tech support |
| E351 | Abnormal Auto Feeder Valve | Medium | Call tech support |
| E352 | APS Sensor Abnormality | Medium | Call tech support |
| E353 | APS Sensor Open/Short | Medium | Call tech support |
| E360 | Abnormal cover opening | Medium | Call tech support |
| E407 | Dom.Hot Water Outlet Sensor | Medium | Call tech support |
| E421 | Dom.Cold Water Inlet Sensor | Medium | Call tech support |
| E434 | Abnormal Water Adjust Valve | Medium | Call tech support |
| E438 | Navien Error Code E438 - Abnormal Operation | Medium | Call tech support |
| E439 | No Dom.Water Flow Detected | Medium | Call tech support |
| E441 | Dom.Hot Water Outlet2 Sensor | Medium | Call tech support |
| E445 | Abnormal Mixing Valve | Medium | Call tech support |
| E480 | BMS Communication Error | Medium | Check wiring |
| E515 | Low Water Flow | Medium | Call tech support |
| E517 | Water Flow Switch Failure | Medium | Call tech support |
| E593 | Abnormal Panel Key | Medium | Call tech support |
| E594 | Condensate Blockage | Medium | Call tech support |
| E615 | PCB Communication Failure | Medium | Call tech support |
| E736 | CH Return Thermistor Failure | Medium | Call tech support |
| E740 | CH Buffer Tank Thermistor | Medium | Call tech support |
| E761 | Pump Aquastat Not Detected | Medium | Call tech support |
| E762 | Dual Venturi Failure | Medium | Call tech support |
| E774 | Abnormal external safety system operation 1 | Medium | Call tech support |
| E775 | Abnormal external safety system operation 2 | Medium | Call tech support |
| E777 | System Error Code | Medium | Call tech support |
| E782 | Internal PCB Fault | Medium | Call tech support |
| E784 | Outdoor Temp Sensor Failure | Medium | Call tech support |
| E786 | Header Thermistor Failure | Medium | Call tech support |
| E788 | Pump Failure | Medium | Call tech support |
| E799 | Leak detected (sensor) | Medium | Call tech support |
| E805 | Abnormal supply air- temp sensor operation for lower limit | Medium | Call tech support |
| E810 | Abnormal circulator operation (inoperable) | Medium | Call tech support |
| E811 | Abnormal circulator operation (inoperable) | Medium | Call tech support |
| E818 | Abnormal return air- temp sensor operation for lower limit | Medium | Call tech support |
| E822 | Overcooling of the air conditioning coil (Evaporator coil). | Medium | Call tech support |
| E860 | Replace the circulator filter with a new one, and then reset the furnace. | Medium | Clean air filter |
| E890 | Abnormal circulator communication | Medium | Check wiring |