Equipment error code

Navien code E003

E003 — ignition failure. The controller could not verify burner ignition after the gas valve opened.

Equipment: water heater
Brand: Navien
Source checked: 2026-03-01

What this code means

E003 — ignition failure. The controller could not verify burner ignition after the gas valve opened.

Source: Navien NPE Series Operation Manual — Error Code E003 · checked 2026-03-01

Which models show it

Navien NPE, NPN, and NHW-A series tankless water heaters with front-panel error display.

What is actually happening

No hot water; panel shows E003. Clicking gas valve without stable flame.

Is it safe to keep running?

Stop demanding hot water after two E003 events.

Shut it down when

Gas odor, flame rollout at viewport, or repeated E003.

What a homeowner can safely check

Gas valve open; other appliances work.
Air filter screen on unit clean per manual.
Intake/exhaust PVC clear.
Power button reset once.

When to stop

Gas smell.
Cannot clear intake filter without manual.

Likely causes ranked

1. Insufficient gas pressure or undersized meter
How a tech confirms: Static and dynamic pressure test under max flow.
Typical repair: $200–$600 · Tankless Water Heater Conversion cost guide
2. Dirty ignition electrode or flame rod
How a tech confirms: Inspect and adjust gap; clean rods.
Typical repair: $185–$400 · Water Heater Replacement cost guide
3. Blocked exhaust or air intake
How a tech confirms: Combustion test; verifies vent lengths.
Typical repair: $210–$550 · Water Heater Replacement cost guide
4. Gas valve or PCB failure
How a tech confirms: Navien diagnostic mode readings; parts swap.
Typical repair: $475–$1,050 · Tankless Water Heater Conversion cost guide

Is this the end of this unit?

PCB and gas valve combo on out-of-warranty Navien — price new unit with labor warranty.

How to clear the code

Navien power button off/on once after gas and vent checks.

Why clearing is not fixing it: E003 clears only after successful ignition sequence.

Which trade to call

Call a licensed plumber who works on water heater equipment. Gas, refrigerant, and combustion faults are not general handyman jobs.

How to find a good plumber

Before you sign a contract for this job, use our guide on how to find a good plumber: verify the licence at the state board, compare three itemized quotes on the same scope, and put permit responsibility and change-order rules in writing.

Read the plumber hire guide Check if your quote is fair Verify licences by state

More codes from this brand

E012 — flame loss

Symptom guide: No Hot Water

FAQ

Navien E003?

Ignition failure per Navien error table.

E003 after gas bill unpaid?

Verify utility service — low pressure mimics ignition fault.

Annual service prevent E003?

Filter and vent inspection reduce ignition and exhaust faults.

E003 repair cost?

$185–$1,050 typical range.

E003 vs Rheem code 1?

Same ignition class — follow Navien docs for E003 steps.

Source

Source — Navien NPE Series Operation Manual — Error Code E003. Checked 2026-03-01.