Navien E004 Error Code: False flame detection
Updated October 2026 · Sourced from Navien documentation
🛑 Turn it off and call a licensed pro
The control detected a flame signal when it should not have one. The manual says to ensure the electrical cord is properly grounded.
Is it safe to keep running? No. Turn it off and get it checked. Flame detection is a safety function. If the code stays after checking the cord, call a licensed technician.
E004 at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| E004 Error code shown on the front panel display | False flame detection | 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.
- Check that the power cord is plugged into a properly grounded outlet.
🛑 Stop and call a licensed pro if
- Flame detection is a safety function. If the code stays after checking the cord, call a licensed technician.
- 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
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