Navien E003 (ignition failure): what to check

Navien display

E003

“Ignition failure”

NPE-A2, NPE-S2, NPN · NPE-2 User's Information Manual, p. 17; NPN User's Information Manual, p. 22
Owner checks, then technician

What it means

E003 means the heater tried to light the burner and failed. NPE-2 heaters have no pilot: an ignition device lights the burner automatically, and the manual says not to try lighting it by hand NPE-2 User’s Information Manual, p. 3. The first remedy in both Navien tables is to make sure the main gas supply valve is open NPE-2 User’s Information Manual, p. 17; NPN User’s Information Manual, p. 22. In the sample error-history screen in the NPE-2 Installation & Operation Manual, E003 carries the hint “Check gas supply” p. 96.

Check these first

Check that the main gas supply valve is open NPE-2 User’s Information Manual, p. 17; NPN User’s Information Manual, p. 22. If you are not sure which valve that is, Navien asks owners to have their installer or plumber show them the gas shut-off valve and how to close it NPE-2 User’s Information Manual, p. 5.
Reset the heater once. On NPE-A2 and NPE-S2 models, press Back NPE-2 User’s Information Manual, p. 10. On NPN models, press Reset on the front panel, or OK on the remote for outdoor models NPN User’s Information Manual, pp. 12, 21.
On NPE-A2 and NPE-S2 models, write down what the error history shows. Press Menu and select 3. Error History to see the 10 most recent errors, newest first; OK opens the details of each one NPE-2 Installation & Operation Manual, p. 96.
If E003 comes back with the valve open, stop there. The manual’s next step is an authorized technician, a licensed professional or Navien Technical Support at 1-800-519-8794 NPE-2 User’s Information Manual, p. 16; NPN User’s Information Manual, p. 21.

When to call a licensed technician

E003 returns after the valve check and a reset.
On NPN models, the table adds a gas type check: the gas manifold and the fuel DIP switch setting must match the gas supplied NPN User’s Information Manual, p. 22. Converting a heater between natural gas and propane takes a Navien conversion kit installed by a qualified service agency NPN Installation and Operation Manual, p. 19; NPE-2 Installation & Operation Manual, p. 108.
Neither code table links E003 to gas pressure or the gas line. These two items are here because Navien reserves both for a licensed professional. Gas pressure at the heater’s inlet must be 3.5–10.5 in. WC for natural gas and 8.0–13 in. WC for propane. Navien says the heater cannot function properly without enough inlet pressure and that only a licensed professional should measure it NPE-2 Installation & Operation Manual, p. 24; NPN Installation and Operation Manual, p. 23. If the reading is out of range, the manual points to the gas supplier or a qualified installer.
Flexible gas lines need an inner diameter large enough for the heater’s BTU input, with no crimps or tight bends, since those restrict gas flow NPE-2 Installation & Operation Manual, p. 21; NPN Installation and Operation Manual, p. 21. Gas connections are for a licensed professional only NPE-2 Installation & Operation Manual, p. 20.
Anything behind the front cover. Navien tells owners not to repair or replace parts unless the user’s manual recommends it NPE-2 User’s Information Manual, p. 6; NPN User’s Information Manual, p. 6.

Notes for different models

The NPE-2 table and the NR-21DU remote manual list only the gas valve check for E003 NPE-2 User’s Information Manual, p. 17; NR-21DU Remote Controller Manual, p. 30. The NPN table adds the manifold and DIP switch check p. 22.

The NPE-2 code table comes from Version 1.0 of the user’s manual (2020). The current NPE-2 Installation & Operation Manual, Version 2.0 (January 2026), has no code table and tells the reader to refer to “Troubleshooting” in the Owner’s Manual instead p. 92.

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