Navien · Water heater
E003 Ignition failure
What this code means
The unit failed to establish a flame when it tried to fire — Navien's dedicated ignition-failure code, distinct from a flame loss after the burner was already lit.
Most likely causes
- Gas supply valve not fully open or gas outage
- Ground wire not properly connected
- Igniter not producing a spark
- Control board sending a false signal (sometimes clears with a full power reset)
What to try first
Confirm the gas valve is fully open and the unit's power cord is grounded; if the gas supply checks out, try unplugging the unit for a full 30 minutes to reset the board before calling for service.
Safety note: if this code returns after one clean reset, stop resetting it — repeated lockouts usually mean a real fault that needs a licensed technician. Never bypass a safety switch.
FAQ
What does Navien error code E003 mean?
Ignition failure. The unit failed to establish a flame when it tried to fire — Navien's dedicated ignition-failure code, distinct from a flame loss after the burner was already lit.
Can I fix Navien code E003 myself?
Usually not. Confirm the gas valve is fully open and the unit's power cord is grounded; if the gas supply checks out, try unplugging the unit for a full 30 minutes to reset the board before calling for service. If the code returns after one reset, it needs a licensed technician.
What causes Navien code E003?
The most common causes are: gas supply valve not fully open or gas outage; ground wire not properly connected; igniter not producing a spark; control board sending a false signal (sometimes clears with a full power reset).
Other Navien water heater codes
All Navien water heater error codes →
Other water heater brands: Rheem · Ruud · Rinnai · Noritz · Takagi · A.O. Smith · Bradford White · State / American · Generic electric · Generic tankless
This information may contain errors or not apply to your exact model — always double-check it against your appliance's own manual before acting. If there's any chance of a gas, fire, electrical, carbon monoxide, or other safety hazard, stop and call a licensed professional or the appropriate agency (e.g. your gas utility) instead of relying on this page alone.