Navien E012: Flame Loss During Operation

Navien error code E012 means flame loss during operation — the burner successfully ignited, then the control board lost its flame signal partway through a heating cycle. It’s the Navien counterpart to Rinnai’s code 12, and the causes overlap closely.

Illustration of an ignition electrode assembly resting disconnected on a workbench.

Likely Causes, Ranked

Low or unstable gas pressure under demand
Pressure drops when other gas appliances fire at the same time.
Dirty or oxidized flame rod
The sensor loses its ability to confirm a flame that’s technically still burning.
Venting or exhaust recirculation issue
Same family of cause as seen on other brands’ flame-loss codes.

Step-by-Step Diagnosis

DIY WITH CAUTION
Power off and inspect/clean the flame rod

Same procedure as E003 — fine sandpaper or emery cloth.
PRO ONLY
Check gas pressure under load (a second appliance running)

A drop under demand, not at rest, is the tell.
DIY WITH CAUTION
Verify vent terminal clearances

Recirculated exhaust can interrupt clean combustion mid-cycle.

FAQ

Is E012 the same as E003?

No — E003 means the flame never established. E012 means it lit, then was lost during the cycle. Different starting point, overlapping fixes.

Written by HotWater Decoded — water heater repair specialists. Technically reviewed by a licensed technician on our team.

Sources

Pattern inferred from Navien’s E-code family and Rinnai’s parallel code-12 documentation