Navien Error Codes: What Each E Code Means and the Fix

By Ray Bennett · Updated 2 October 2026 · 5 min read · Navien NPE-2 User's Information Manual, error code chart

Navien Error Codes: What Each E Code Means and the Fix

Short answer

E003 is ignition failure and Navien's first fix is the gas valve being open. E012 is flame loss, often a dirty intake air filter. E016 and E030 are overheating, which Navien fixes with a clean inlet water filter and a flush. Most other codes go to Navien's technical support, and Navien's own chart says so.

A Navien tankless water heater shows a code starting with E on its front panel when something is wrong. A handful of them have a fix you can do yourself, and Navien’s own chart tells you which.

Everything on this page comes from Navien’s user’s information manual for the NPE-2 series. Many older Navien heaters use the same numbers, but the chart in your own manual is the one to trust.

Before you start

What to carry: a torch and a pen. Ten minutes for most codes, longer for a flush.

Gas or electric? These are codes for Navien gas tankless heaters. The NPE-2 series is a condensing gas heater.

Write the code down first. Support will want it, and a reset clears it from the panel.

To reset, Navien says to press the Back button on the front panel. For minor problems that alone may clear it.

Three things before trying any fix. Smell gas? Stop. Do not reset or light anything. Leave and call from outside.

Navien’s own words on this chart: if resetting and the suggested remedies do not solve it, contact an authorised technician, a licensed professional or Navien’s technical support. Most codes on the list say exactly that.

E773 means the wrong gas. A heater fed a different gas from the one it was set up for is not a reset job. Leave it off until it is checked.

The codes an owner can often fix

Navien's chart gives an owner's fix for only a few codes, and they come down to three things: gas on, filters clean, and a flush.

Check 1

Work Navien's own first fix

E003, ignition failure. Navien’s first check: make sure the main gas supply valve is open. After gas work, air in the line causes this too, and a few tries may be needed.

E012, flame loss. Clean the intake air filter, and make sure the electrical cord is properly grounded.

E109, fan motor, and E110, abnormal air pressure. Clean the intake air filter. For E110, also make sure the exhaust pipe is free of obstructions such as a nest, leaves or snow.

E016, heat exchanger overheating, and E030, exhaust overheating. Clean the cold water inlet filter and flush the heat exchanger. Navien’s manual gives the E030 shutdown point as a flue temperature above 149 degrees.

E004 and E515. Navien points both at grounding: make sure the electrical cord is properly grounded.

E760, the flushing or service alarm. Not a fault. Navien says to contact the installer for routine service: how a tankless heater is flushed.

E788, gas type mismatch. The gas type set on the panel does not match its DIP switch. Navien says to check the supplied gas and match the two settings.

The full list

Code	What Navien calls it	What Navien says to do
E003	Ignition failure	Make sure the main gas valve is open
E004	False flame detection	Check the cord is grounded
E012	Flame loss	Clean the intake air filter, check grounding
E016	Heat exchanger overheating	Clean the inlet filter, flush
E030	Exhaust overheating	Clean the inlet filter, flush
E031	Burner overheating	Technical support
E046	Limit control	Technical support
E047	Exhaust thermostat sensor	Technical support
E060	Dual venturi	Technical support
E109	Fan motor	Clean the intake air filter
E110	Abnormal air pressure	Clear the exhaust, clean the air filter
E407	Hot water outlet sensor	Technical support
E421, E432	Cold water inlet sensors	Technical support
E434	Water adjustment valve	Technical support
E438	Circulation pump, with an air handler	Check the pump runs
E439	Flow sensor	Technical support
E441	Hot water inlet sensor	Technical support
E445	Bypass mixing valve	Technical support
E515	Circuit board	Check the cord is grounded
E517	DIP switch setting	Technical support
E593, E594, E615	Front panel key, memory	Technical support
E736, E782	Cascade or panel communication	Technical support
E740, E785	Sensors used with an air handler	Technical support
E760	Flushing or service alarm	Book routine service
E762	Vent pipe not properly inserted	Technical support
E773	Using the wrong gas	Technical support
E788	Gas type settings do not match	Match the panel and DIP switch

No code, but no hot water

Navien's own checklist for hot water that never arrives or turns cold. The flow rate is the one people miss.

Check 2

Work Navien's basic problem list

The cold water inlet filter. Navien lists it first for both no water and cold water. A clogged screen starves the heater.

The tap open wide enough. Navien says to draw at least half a gallon a minute through the heater. A tap barely open, or a low flow shower head, can sit below that and the burner never lights.

The shut off valves. Both the hot and cold valves at the heater must be open.

Frozen. A heater in a cold space can freeze, and Navien lists it among the causes of no water at all: what to do with pipes that have frozen.

A recirculation system. If you have one, Navien asks whether there is a check valve on the return line. Without it, cold water mixes into the hot.

Water not hot enough, or too hot. Check the set temperature first: what temperature to set a water heater.

When it needs support

Check 3

Know when to stop

Every sensor, valve and board code. Navien’s chart sends them all to technical support, and they need a meter and the right part.

E003 or E012 that return with the gas on and the filter clean. Gas pressure, the igniter and the flame rod come next, which is technician work.

E016 or E030 soon after a flush. Overheating that comes straight back points past the scale, at the flow or the venting.

Anything that clears and returns. The cheap cause was not the real one.

Questions people ask

How do I reset a Navien?

Navien’s manual says to press the Back button on the front panel. If the cause is still there, the code comes back.

Where is the intake air filter?

On the heater itself, where the combustion air comes in. Your manual shows its position for your model. It is a quick clean and it clears several codes.

What does E760 actually mean?

It is a reminder rather than a failure: the heater is due its routine flush and service.

Why does it go cold when I turn the tap down?

Navien needs at least half a gallon a minute of flow. Turn the tap down far enough and the burner switches off.

Is E003 serious?

Usually it is the gas: a closed valve, an empty propane tank, or air in the line after work. If the gas is definitely on and it keeps happening, it needs a technician.

My code is not on this list.

Other Navien series, combi boilers and newer models have codes of their own. The error code chart in your own manual lists every code your heater uses.