What does error code E003 mean on a Navien tankless water heater?

Ignition failure. The heater failed to ignite.

Can I fix Navien code E003 myself?

Start with these safe checks: Make sure the main gas supply valve to the heater is open, and for propane, the tank has fuel. If it continues, contact Navien technical support or a qualified gas technician. If you smell gas, leave and call your gas supplier from outside.

When should I call a technician for code E003?

If it continues, contact Navien technical support or a qualified gas technician. If you smell gas, leave and call your gas supplier from outside. Smell gas? Leave right away, don't touch light switches or phones inside, and call your gas utility or 911 from outside. Never open a gas valve, burner, gas line, vent or flue connection, or bypass a safety switch. Repeated lockouts, scorching, soot, or a CO alarm mean shut it off and call a licensed gas technician.

Navien Tankless Water Heater Error Code E003: Ignition failure

What E003 means

The heater failed to ignite.

Likely causes

Gas supply valve closed
Empty propane tank
Gas supply problem

Safe first checks

Make sure the main gas supply valve to the heater is open, and for propane, the tank has fuel.

When to stop

If it continues, contact Navien technical support or a qualified gas technician. If you smell gas, leave and call your gas supplier from outside.

Checked against: Navien NPE-2 user's information manual: understanding error codes. Codes can differ by model and year, so confirm with your owner's manual.