BoilerFaultCodesNavien E02 Fault Code
The Navien E02 fault code means: your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.. It appears on 7 Navien models in our database.
Technical description: The pressure is lower than the minimum pressure set (1 bar by default)
DIY fix possible
Locate the filling loop (usually two silver flexible hoses) underneath the boiler.Open the valves slowly to allow mains cold water into the system.Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (typically 1.0 to 1.5 bar).Close both valves tightly to stop the flow of water.
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Gas Safe Register →Navien models that show the E02 fault code
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Source
Navien E02 fault code information on this page is sourced and cross-checked against the official Navien service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026