DIY Error Codes

Navien NPE-2 tankless water heater Error E012

The flame went out during operation. Navien lists grounding and the cold water inlet filter as the checks.

Have the cord's grounding confirmed and clean the cold water inlet filter.

Start the fix →When to call a pro ↓
Full answer & models

Navien E012 on the NPE-2 means: flame loss. Have the cord's grounding confirmed and clean the cold water inlet filter.

Applies to: NPE-180A2NPE-210A2NPE-240A2NPE-180S2NPE-210S2NPE-240S2
Also searched as: Navien error E012, Navien E012, Navien error code 012, Navien 012 code

Gas appliance. Power off and let it cool before any maintenance.
Why
If you smell gas: do not try to light any appliance, do not touch any electrical switch, and do not use any phone in your building. Leave and call your gas supplier from a neighbor's phone; if you cannot reach them, call the fire department. Navien: turn the water heater off and disconnect the power supply before maintenance. It can stay hot for several minutes after it is turned off; wait until it cools to avoid burns. Water at or above 125 °F (52 °C) can cause instant scalding, severe burns, or death.

What E012 means

The flame went out during operation. Navien lists grounding and the cold water inlet filter as the checks.

More detail
Navien's error-code chart (section 5.2) lists E012 as "flame loss". If the listed remedies do not resolve the problem, Navien says to contact Technical Support.

5-minute checks

Fix it step by step

Step 1 of 3

  1. Confirm the power cord is properly grounded

    • 5 min
    • None
    • Caution

    Safety: Gas appliance. Power off and let it cool before any maintenance.

    If you are not sure the outlet is grounded, have an electrician check it.

    More detail

    Confirm the power cord is properly grounded.

    Navien chart, E012 flame loss: ensure that the electrical cord is properly grounded.

    Did the code clear?

  2. Clean the cold water inlet filter

    • 30 min
    • Bucket, Soft brush
    • DIY

    Safety: Gas appliance. Power off and let it cool before any maintenance.

    Drain the heater, then rinse and brush the inlet filter.

    More detail

    Clean the cold water inlet filter.

    Navien sections 4.2 and 4.4: press Power off, close the gas valve, close the cold water supply valve, open hot faucets to drain the lines, put a bucket under the heater and remove the inlet filter (and the recirculation inlet filter and pump drain plug on A2 models). Rinse the filter under cold running water, brush if needed, reinstall and tighten, then refill by reversing the steps.

    Did the code clear?

  3. Call a licensed pro

    • Decision
    • None
    • Pro decision

    Stop here and book a qualified technician.

    More detail

    Call a licensed pro.

    If E012 continues after these checks, have a licensed technician inspect the gas supply and burner.

    Still showing E012?Need a pro → call a pro

Code cleared. Nice work.

Watch the display for a day to make sure it stays clear.

Back to top

Fixed after any step? Watch the display for a day to make sure it stays clear. Still E012 after step 3? call a pro.

Call a pro if…

  • E012 returns after the filter is clean and grounding is confirmed.
  • You are unsure whether the outlet is grounded.
  • You smell gas.

FAQ

What does Navien E012 mean?

Flame loss, per the NPE-2 error-code chart.

Source: Navien NPE-2 User's Information Manual (NPE-A2/NPE-S2), Section 5.2 Understanding Error Codes, Sections 4.2-4.5 Maintenance. Written by the DIY Error Codes team. Updated 2026-10-16. DIY Error Codes is independent and not affiliated with or endorsed by Navien.