Navien Tankless Water Heater Error Code E012: Meaning & How to Fix It

By the ErrorCodePro Editorial Team · Last reviewed October 20, 2026

Navien tankless water heater error code E012 means: The flame was lost during operation. [1] Keep using it? No hot water until it's resolved. Don't keep resetting it.. Start with the owner checks below, beginning with: clean the intake air filter.

Smell gas? Leave the building now. Do not touch light switches, phones or appliances inside. Call your gas utility or 911 from outside. CO alarm sounding or headache, dizziness or nausea? Get everyone outside and call 911. Gas valves, burners, venting and wiring are for a licensed technician only. See our safety policy.

Quick facts

Code	E012
Also shown as	None listed by the manufacturer
Brand / appliance	Navien tankless water heater (npe-2 condensing tankless water heaters)
System	Heating
Official meaning	The flame was lost during operation. [1]
Keep using it?	No hot water until it's resolved. Don't keep resetting it.
DIY-safe?	Owner checks only (listed below)
Support	Navien Technical Support, 1-800-519-8794

On this page: Meaning · Steps · Parts · When to call a technician · Related codes · FAQ

What error code E012 means on a Navien tankless water heater

The flame was lost during operation. [1]

This is a heating code. Codes and wording can vary by model, so check your owner's manual for your model number.

How to fix Navien tankless water heater error code E012 (safe owner checks)

Owner checks only: on heating, cooling and water-heating equipment, limit yourself to reading the code and checking the thermostat, breaker and service switch, air filter, condensate drain, that the gas supply valve is open (no disassembly) and that vent terminals are clear of snow or debris. Reset power only if your manual allows it.

Safety first: disconnect power before you remove any panel or reach into the sump or drum. Do not touch wiring, the control board or the motor. If you see water near electrical parts, stop and call a technician. These steps are based on Navien's published guidance [1], rewritten for clarity.

Clean the intake air filter. Clean the intake air filter (see the User's Information Manual).
Check grounding. Make sure the power cord is plugged into a properly grounded outlet.
Check the gas supply. Make sure the gas supply valve to the water heater is open (handle in line with the pipe) and other gas appliances work. Don't take anything apart.

Parts that may be involved

Exact parts depend on your model number. This page lists part types only, never part numbers.

No specific part is implied by the manufacturer's guidance for this code.

When to call a technician

Gas pressure, gas valve, igniter, flame rod, venting or combustion problems: licensed plumber or gas technician
Gas valves, burners, igniters, flame sensors, venting/flue or CO concerns: licensed HVAC technician or plumber
Refrigerant work: EPA 608-certified technician only
Smell of gas: leave and call the gas utility or 911
Anything involving wiring, the control board, the motor or the water valve electrics
The appliance is under warranty: contact Navien Technical Support, 1-800-519-8794 first

Frequently asked questions

What does error code E012 mean on a Navien tankless water heater?

Navien lists E012 as follows: The flame was lost during operation.

Is it safe to keep using the tankless water heater with E012?

No hot water until it's resolved. Don't keep resetting it..

Can I fix Navien tankless water heater error E012 myself?

Only with the owner checks on this page, starting with: clean the intake air filter. If it persists, call a technician or Navien Technical Support, 1-800-519-8794.

Sources

https://www.navieninc.com/downloads/npe-2-user-s-information-manual-en/download (official)

Last reviewed: October 20, 2026. ErrorCodePro is not affiliated with Navien.