Navien displays three-digit numeric error codes on the controller and in the NaviLink app. The codes are consistent across NPE tankless, NCB combi boilers, NFC fire-tube combi, and NHB heating boilers — though some codes are specific to combi (E110 communication) or specific to condensing units (E041 condensate). Older Navien units sometimes show the same codes prefixed with "E" (E003 vs 003) — these are the same code, displayed differently by controller generation.
The top codes you'll actually see
| Code | Meaning | Most common cause |
|---|---|---|
| 003 / E003 | No flame / ignition failure | Gas supply / igniter / flame rod |
| 012 / E012 | Flame failure during operation | Dirty flame rod / vent |
| 016 / E016 | Overheat protection | Scaled heat exchanger |
| 030 / E030 | Combustion fan fault | Fan motor / pressure switch |
| 041 / E041 | Condensate drain blocked | Trap or drain line |
Full numeric reference
| Code | Description |
|---|---|
| 002 | Unit not initialized / setup mode |
| 003 | Ignition failure / no flame |
| 004 | False flame signal |
| 010 | Air pressure / venting abnormality |
| 012 | Flame failure during operation |
| 015 | Control board (PCB) fault |
| 016 | Overheat (heat exchanger or burner) |
| 020 | Inlet thermistor |
| 021 | Outlet thermistor |
| 022 | Heat exchanger thermistor |
| 023 | DHW inlet thermistor |
| 027 | Mixing valve fault (combi) |
| 030 | Combustion fan motor |
| 032 | Condensate pressure switch |
| 034 | Combustion air pressure switch |
| 038 | 2-way valve / 3-way diverter (combi) |
| 041 | Condensate drain blocked |
| 043 | Flow sensor (DHW) |
| 046 | Boiler return temp too high (combi) |
| 060 | Gas valve circuit |
| 070 | Heat exchanger high limit |
| 099 | Combustion abnormality |
| 109 | Remote controller communication |
| 110 | Control communication (master-slave cascade or remote) |
| 114 | NaviLink Wi-Fi module communication |
| 351-394 | Various sensor faults (specific by code) |
How to reset
Three reset levels:
- Level 1 — controller reset: press the reset button (controller varies — usually a dedicated button or hold On/Off for 3 seconds)
- Level 2 — power cycle: turn off at wall outlet or breaker, wait 30 seconds, restore. Clears all running state
- Level 3 — factory reset: service-menu only. Requires installer password. Resets all configured settings
If the code returns within 60 seconds of reset, the underlying fault is active — escalate to the specific code's diagnostic walkthrough.
Bottom line
Don't replace parts based on the code alone. Each code page above contains the diagnostic sequence to isolate the specific failed component. For cases without a displayed code, see general troubleshooting.