ErrorCodePro · Appliance Error CodesNavien Tankless Water Heater Error Codes: Full List & Meanings
Every Navien tankless water heater error code we have verified against Navien's own support pages, with its official meaning. This list covers npe-2 condensing tankless water heaters. Codes vary by model, so confirm in your owner's manual. Support: Navien Technical Support, 1-800-519-8794.
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.
Codes by system
Heating
Venting / airflow
Motor / drive
All Navien tankless water heater error codes
Codes marked "Reset only" or "Service" have no separate page because the manufacturer publishes no owner fix beyond a reset or a service call.
| Code | Official meaning | System | Owner action |
|---|---|---|---|
| E003 | The burner failed to ignite. | Heating | Owner checks |
| E012 | The flame was lost during operation. | Heating | Owner checks |
| E016 | The heat exchanger is overheating, often from a clogged inlet filter or scale. | Heating | Owner checks |
| E030 | The heater shuts down when the flue temperature exceeds 149°F (65°C). | Venting / airflow | Owner checks |
| E110 | Abnormal air pressure in the combustion air system. | Venting / airflow | Owner checks |
| E109 | The fan motor isn't operating normally. | Motor / drive | Owner checks |
| E004 | The manufacturer lists E004 as: false flame detection; check the cord is grounded. Contact Navien Technical Support, 1-800-519-8794. | Heating | Service |
| E031 | The manufacturer lists E031 as: burner overheating. Contact Navien Technical Support, 1-800-519-8794. | Heating | Service |
| E046 | The manufacturer lists E046 as: limit control. Contact Navien Technical Support, 1-800-519-8794. | Heating | Service |
| E047 | The manufacturer lists E047 as: exhaust thermistor open or short. Contact Navien Technical Support, 1-800-519-8794. | Sensors | Service |
| E060 | The manufacturer lists E060 as: dual venturi. Contact Navien Technical Support, 1-800-519-8794. | Venting / airflow | Service |
| E407 | The manufacturer lists E407 as: hot water outlet thermistor. Contact Navien Technical Support, 1-800-519-8794. | Sensors | Service |
| E421 | The manufacturer lists E421 as: cold water inlet 1 thermistor. Contact Navien Technical Support, 1-800-519-8794. | Sensors | Service |
| E432 | The manufacturer lists E432 as: cold water inlet 2 thermistor. Contact Navien Technical Support, 1-800-519-8794. | Sensors | Service |
| E434 | The manufacturer lists E434 as: water adjustment valve. Contact Navien Technical Support, 1-800-519-8794. | Water fill | Service |
| E438 | The manufacturer lists E438 as: circulation pump (with AHU); check it runs. Contact Navien Technical Support, 1-800-519-8794. | Motor / drive | Service |
| E439 | The manufacturer lists E439 as: flow sensor. Contact Navien Technical Support, 1-800-519-8794. | Sensors | Service |
| E441 | The manufacturer lists E441 as: hot water inlet 2 thermistor. Contact Navien Technical Support, 1-800-519-8794. | Sensors | Service |
| E445 | The manufacturer lists E445 as: bypass mixing valve. Contact Navien Technical Support, 1-800-519-8794. | Water fill | Service |
| E515 | The manufacturer lists E515 as: PCB; check the cord is grounded. Contact Navien Technical Support, 1-800-519-8794. | Control / electronics | Service |
| E517 | The manufacturer lists E517 as: DIP switch setting. Contact Navien Technical Support, 1-800-519-8794. | Control / electronics | Service |
| E593 | The manufacturer lists E593 as: front panel key. Contact Navien Technical Support, 1-800-519-8794. | Control / electronics | Service |
| E594 | The manufacturer lists E594 as: EEPROM. Contact Navien Technical Support, 1-800-519-8794. | Control / electronics | Service |
| E615 | The manufacturer lists E615 as: input and memory. Contact Navien Technical Support, 1-800-519-8794. | Control / electronics | Service |
| E736 | The manufacturer lists E736 as: cascade communication. Contact Navien Technical Support, 1-800-519-8794. | Control / electronics | Service |
| E740 | The manufacturer lists E740 as: outdoor temperature sensor (with AHU). Contact Navien Technical Support, 1-800-519-8794. | Sensors | Service |
| E760 | The manufacturer lists E760 as: flushing/service alarm; the installer should do routine service. Contact Navien Technical Support, 1-800-519-8794. | Status / reminder | Service |
| E762 | The manufacturer lists E762 as: vent pipe not properly inserted (CO risk, technician). Contact Navien Technical Support, 1-800-519-8794. | Venting / airflow | Service |
| E773 | The manufacturer lists E773 as: using the wrong gas (technician). Contact Navien Technical Support, 1-800-519-8794. | Heating | Service |
| E782 | The manufacturer lists E782 as: main panel communication. Contact Navien Technical Support, 1-800-519-8794. | Control / electronics | Service |
| E785 | The manufacturer lists E785 as: flow switch/sensor (with AHU). Contact Navien Technical Support, 1-800-519-8794. | Sensors | Service |
| E788 | The manufacturer lists E788 as: gas type mismatch with DIP switch setting (technician). Contact Navien Technical Support, 1-800-519-8794. | Heating | Service |
Symptoms
Sources
Last reviewed: October 20, 2026. ErrorCodePro is not affiliated with Navien.