Navien E003 Error Code: Ignition failure
Updated October 2026 · Sourced from Navien documentation
The water heater could not light the burner. The manual's only listed action is to make sure the main gas supply valve is open.
Is it safe to keep running? Check the steps below first. If the main gas valve is open and the code returns, call a licensed gas technician. Do not try to repair gas or ignition parts yourself.
E003 at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| E003 Error code shown on the front panel display | Ignition failure | NPE-180A2, NPE-210A2, NPE-240A2, NPE-180S2, NPE-210S2, NPE-240S2 condensing tankless water heaters |
Check this first
Only steps a homeowner can do safely. Do not open electrical panels or the burner area.
- Make sure the main gas supply valve to the water heater is fully open.
- If you smell gas, do not touch switches, leave the building and call your gas supplier.
- Turn the unit off with the Power button, wait a minute, then turn it back on to see if the code clears.
🛑 Stop and call a licensed pro if
- If the main gas valve is open and the code returns, call a licensed gas technician. Do not try to repair gas or ignition parts yourself.
- You smell gas. Leave the house, do not touch switches, and call your gas utility from outside.
- Codes for flame failure, overheating, venting or the control board that return after one reset.
- Water leaking from the heater, the relief valve discharging, or scorching around the burner area.
- A carbon monoxide alarm sounds. Get everyone outside and call 911 or the fire department.
Safe first steps for any Navien code
- Write down the exact code shown on the controller or the number of status light flashes.
- Turn the water heater power off and back on (or press the reset button the manual describes) once. If the code comes back, stop resetting.
- Make sure the gas supply valve to the heater is open and other gas appliances in the home are working.
- Make sure the cold water supply valve is fully open and hot water taps are not partly closed.
- Look at the outside vent terminal for snow, ice, leaves or anything blocking it (look only).
Source: Navien NPE Condensing Water Heaters User's Information Manual (NPE-2, rev 201202), 5.2 Understanding Error Codes, p.17. Codes are series-specific, so your unit's own manual is the final word. Reviewed October 2026.
Ryan Giles · Red Seal Certified Plumber · Ask a plumber · Ask an HVAC technician