BoilerFaultCodesGrant E01 Fault Code
The Grant E01 fault code means: your boiler's main internal computer has encountered a processing error and cannot safely operate.. It appears on 2 Grant models in our database.
Technical description: Internal control fault
What causes the Grant E01 fault?
This fault occurs when the boiler's main control board experiences a critical electronic failure, meaning it can no longer communicate with the internal sensors or components. The most common reason is a component failure on the circuitry itself, often caused by age, a power surge, or moisture ingress affecting the delicate electronics.
This fault is slightly more common during the winter months when heating systems are under constant load and electrical components are more susceptible to failing under continuous thermal stress.
DIY fix possible
Press the reset button on the control panel onceTurn the main power switch to the boiler off, wait 30 seconds, and turn it back onEnsure the boiler has not been subject to a recent power surge or lightning strike
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Gas Safe Register →Grant models that show the E01 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Grant E01 fault code information on this page is sourced and cross-checked against the official Grant service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026