DIY Error Codes

Navien NPE-2 tankless water heater Error E003

The burner failed to light. Navien's listed action: make sure the main gas supply valve is open.

Check that the gas valve is open. If it is and E003 returns, call a licensed pro.

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

Navien E003 on the NPE-2 means: ignition failure. Check that the gas valve is open. If it is and E003 returns, call a licensed pro.

Applies to: NPE-180A2NPE-210A2NPE-240A2NPE-180S2NPE-210S2NPE-240S2
Also searched as: Navien error E003, Navien E003, Navien error code 003, Navien 003 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 E003 means

The burner failed to light. Navien's listed action: make sure the main gas supply valve is open.

More detail
Navien's error-code chart (section 5.2) lists E003 as "ignition failure". 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 2

  1. Make sure the main gas valve is open

    • 2 min
    • None
    • DIY

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

    Navien's listed action for E003.

    More detail

    Make sure the main gas valve is open.

    Navien chart, E003 ignition failure: ensure that the main gas supply valve is open.

    Did the code clear?

  2. Call a licensed pro

    • Decision
    • None
    • Pro decision

    Stop here and book a qualified technician.

    More detail

    Call a licensed pro.

    If the valve is open and E003 keeps returning, the gas supply, ignition or burner needs a qualified gas technician. Do not open the sealed combustion area yourself.

    Still showing E003?Need a pro → call a pro

Code cleared. Nice work.

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

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Fixed after any step? Watch the display for a day to make sure it stays clear. Still E003 after step 2? call a pro.

Call a pro if…

  • You smell gas (leave first, then call your gas supplier).
  • The gas valve is open and E003 comes back.
  • You would need to open the heater or test gas pressure.

FAQ

What does Navien E003 mean?

Ignition failure, per Navien's NPE-2 error-code chart.

What does Navien say to check?

That the main gas supply valve is open. Beyond that, contact Navien Technical Support or a licensed pro.

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.