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ErrBase

Navien Waterheater Error Codes

All Navien waterheater error codes with step-by-step troubleshooting, multimeter specs, and OEM part numbers.

10 error codes

CodeMeaning
E001The unit failed to establish a flame on the first ignition attempt. E001 is an early-stage ignition fault that precedes E003, which fires after all 3 attempts fail.
highbeginner
E003The unit attempted to ignite 3 times and failed to detect a flame on any attempt. The gas valve, igniter, and flame rod are the primary components to inspect.
highintermediate
E012The burner flame was established successfully but was lost while the unit was actively heating water. This is distinct from E003, which means ignition never occurred at all.
highintermediate
E110The unit detected an exhaust or air supply restriction. E110-01 indicates an external vent termination blockage; E110-02 indicates an internal air/exhaust pressure imbalance.
highbeginner
E302The PCB detected a flame signal from the flame rod when the gas valve is confirmed closed and the unit should be off. This is a safety lockout that prevents the unit from operating until the false signal is resolved.
moderateintermediate
E762The outlet water temperature exceeded 190 degrees Fahrenheit (87.7 degrees Celsius), triggering a high-limit safety lockout. The unit shuts off to prevent scalding and thermal damage to components.
highintermediate
E773The exhaust gas temperature exceeded the safe thermal limit. A thermal fuse or high-limit sensor in the exhaust path tripped due to excessive heat, causing a safety lockout.
highintermediate
HUBReference hub covering all Navien NPE and NCB series error codes with diagnosis and repair guidance.
lowbeginner
NO-HOT-WATERError Codes and Flow Sensor Fix
mediumintermediate
RESETGuide covering all three reset methods for Navien NPE and NCB series: soft reset via Info button, hard reset via power cycle, and factory reset via controller menu.
lowbeginner