Navien tankless water heater error codes
Complete list of 37 checked codes for Navien tankless water heaters, with what each code means and whether you can fix it yourself.
Reference sheet from https://faultcodeindex.com/navien/tankless-water-heater/ (checked against Navien manuals).
| Code | Meaning | What you can do |
|---|---|---|
| E003 | Ignition failure | Safe checks first, then a pro |
| E004 | False flame detected | Safe checks first, then a pro |
| E012 | Flame lost | Safe checks first, then a pro |
| E016 | Heat exchanger overheated | Safe checks first, then a pro |
| E030 | Exhaust too hot | Safe checks first, then a pro |
| E031 | Burner overheated | Call a pro |
| E046 | Limit control fault | Call a pro |
| E047 | Exhaust temperature sensor fault | Call a pro |
| E056 | Modulating gas valve fault | Call a pro |
| E060 | Dual venturi fault | Call a pro |
| E109 | Fan motor fault | Safe checks first, then a pro |
| E110 | Abnormal air pressure (blocked vent or intake filter) | Safe checks first, then a pro |
| E127 | Air volume sensor fault | Call a pro |
| E157 | Air volume control fault | Call a pro |
| E170 | Freeze protection heater fault | Call a pro |
| E407 | Hot water outlet temperature sensor fault | Call a pro |
| E421 | Cold water inlet temperature sensor 1 fault | Call a pro |
| E432 | Cold water inlet temperature sensor 2 fault | Call a pro |
| E434 | Water adjustment valve fault | Call a pro |
| E438 | Circulation pump fault | Safe checks first, then a pro |
| E439 | Flow sensor fault | Call a pro |
| E441 | Hot water inlet temperature sensor 2 fault | Call a pro |
| E445 | Bypass mixing valve fault | Call a pro |
| E515 | Circuit board fault | Safe checks first, then a pro |
| E517 | DIP switch setting error | Call a pro |
| E593 | Front panel button fault | Call a pro |
| E594 | Memory chip (EEPROM) fault | Call a pro |
| E615 | Input and memory fault | Call a pro |
| E736 | Cascade communication fault | Call a pro |
| E740 | Outdoor temperature sensor fault | Call a pro |
| E760 | Flushing or service reminder | Call a pro |
| E762 | Vent pipe not fully inserted | Call a pro |
| E773 | Wrong gas type detected or gas connection fault (depends on model) | Call a pro |
| E782 | Main panel communication fault | Call a pro |
| E785 | Flow switch or sensor fault | Call a pro |
| E786 | Panel connection fault | Call a pro |
| E788 | Gas type setting mismatch | Call a pro |