What does Navien error code E003 mean?

E003 means ignition failure. That is the label in Navien's error code chart for NPE condensing models. When you open a hot tap, the fan starts, the igniter sparks and the gas valve opens. If the control board does not see a flame, it shuts down the gas and displays E003.

Compare it with the codes next to it. E003 is a burner that never lit. E012 is flame loss, where the burner lit and then went out. E004 is false flame detection, where the heater thinks there is a flame when there should not be. Navien lists a grounding check for E004 and for E012 as well. Reading which one you have matters because each points at a different part of the system.

Do the gas smell check before anything else. Navien's manual, like every gas appliance manual, says that if you smell gas you should not try to light any appliance, should not touch electrical switches and should not use a phone in the building. Leave and call the gas supplier. In the Phoenix area, Southwest Gas asks you to get out, leave the doors open, and call 911 and 877-860-6020 from a safe spot. Skip the code until the gas is dealt with.

With no smell, follow Navien's order:

1. 1Open the gas valve. Confirm the main gas shutoff to the water heater is fully open. This is the fix Navien lists for E003.
2. 2Reset. Press the Reset button on the front panel. Navien says resetting may clear a minor problem, and points you to the troubleshooting chart or Technical Support at 1-800-519-8794 if it does not.
3. 3Try a hot tap. Open one and give the heater a full minute. Watch whether it lights and holds.
4. 4Check other gas appliances. If the range or furnace is also weak or out, the trouble is in the supply, not in the heater.
5. 5Propane homes. Make sure the tank has fuel.

If it lights and runs normally, note the date and watch it. If E003 returns the same day, do not keep pressing Reset. Repeating a failed ignition does not fix it.

A repeating E003 comes down to four areas, and only the first is a homeowner check.

• The gas valve is not fully open. Navien's chart lists the main gas supply valve as the E003 fix, so confirm it is open all the way and did not get bumped.
• Low or unstable gas pressure. The heater needs steady pressure to light. Navien's installation manual says the inlet gas pressure must stay between 3.5 and 10.5 inches of water column on natural gas, and between 8.0 and 13 inches on propane. It also says measuring that pressure should be done by a licensed professional only. A gas line that is too small, a long run, or other appliances drawing at the same time can pull pressure below the minimum.
• Ignition parts. A worn igniter or a dirty flame rod can prevent a clean start, the same as on other brands of gas tankless heater. This is a technician job, since the burner compartment has both gas and high voltage.
• Air and exhaust. A blocked intake filter or exhaust restricts airflow, and a burner that cannot breathe cannot light reliably. Navien lists cleaning the intake air filter as a fix for E012 and for E110, its abnormal air pressure code, and clearing the exhaust pipe as a fix for E110. Those same restrictions can also affect ignition.

New installs deserve a special note. If E003 appears right after installation or after gas work, air can be trapped in the line, or the gas line may be undersized for the heater and everything else on it. Both are installer items. A properly sized gas line is part of the job.

### What do the other common Navien codes mean?

Navien's chart for the NPE condensing line is short, and a few entries matter most here. Here is what the manual says for each, so you can tell whether E003 is really your code:

• E012, flame loss. Clean the intake air filter and make sure the electrical cord is properly grounded.
• E016, overheating of the heat exchanger. Turn the system off for at least 30 minutes, then restart it. Clean the cold water inlet filter and flush the heat exchanger. Hard water scale can build up on a heat exchanger, which is why flushing is part of the fix and why Phoenix owners should follow a flushing schedule.
• E110, abnormal air pressure. Make sure the exhaust pipe is free of obstructions and clean the intake air filter.
• E515, control board. Make sure the electrical cord is properly grounded.
• Anything else on the chart. Navien tells you to contact Technical Support at 1-800-519-8794, or an authorized technician.

Notice how often the manual points to two simple items: a clean filter and a good ground. Both are quick to check and worth confirming before someone replaces a part.

### How long should I wait between resets?

Navien's manual describes the reset as a try for minor problems, and says that if resetting does not solve the problem you should read the chart or call Technical Support. Give the heater a full hot water run after a reset. Two failed resets in a row is your sign to stop and get the gas pressure and ignition parts tested.

A technician measures inlet gas pressure while the heater fires, and compares it to Navien's range. They check the gas type setting against your fuel, inspect the igniter and flame rod, and clean the burner if needed. They check that the electrical supply is properly grounded, because Navien lists grounding as a fix for both E004 and E012. They also inspect the vent and the intake air filter.

Call if E003 returns after a reset, if you have no hot water and cannot open the gas valve any further, if there is any gas smell, or if the problem began right after new gas work. Our licensed, insured team at HQ Plumbing and Air handles gas tankless heaters day or night. Estimates are free and the price is set up front, before work starts.

Two prevention habits help. Clean the intake air filter and the cold water inlet filter as the Navien manual describes, and flush the heat exchanger. Phoenix water is hard, so scale collects faster here. Our page on descaling a tankless water heater in Phoenix explains timing. Neither task is an E003 fix by itself, but a heater kept clean has fewer faults to chase.

If your problem is a different brand, see our pages on Rinnai error code 11, which is Rinnai's no ignition code, and Rinnai error code 12, its flame failure code. They work the same way, with different numbers.

For the two codes that point at air filters and overheating instead, see our page on Navien error codes E012 and E016.

On a Noritz, ignition failure is code 11, covered on our page on Noritz error codes 11, 90 and 99.