BoilerFaultCodesNavien E002 Fault Code
The Navien E002 fault code means: your boiler has stopped working because the water pressure inside the heating system has dropped below the required level.. It appears on 6 Navien models in our database.
Technical description: Low Water Pressure
DIY fix possible
Locate the filling loop (a flexible metal hose) connected to the pipes underneath your boiler.Open the valves on the filling loop to allow cold mains water into the system.Watch the pressure gauge on the boiler until the needle reaches the green zone (usually between 1 and 1.5 bar) and then firmly close both valves.
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Gas Safe Register →Navien models that show the E002 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Navien E002 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