BoilerFaultCodesIntergas E31 Fault Code
The Intergas E31 fault code means: your boiler has detected that the internal temperature sensors have been mixed up or are reading in the wrong order, preventing it from heating your water safely.. It appears on 6 Intergas models in our database.
Technical description: Flow and return sensors swapped
What causes the Intergas E31 fault?
This fault occurs when the boiler's control board detects that the temperature readings for the outgoing and incoming water pipes are reversed. It usually happens because the physical sensors have been clipped onto the wrong pipes during a repair, or the internal wiring harness has been connected incorrectly. In some cases, a faulty sensor sending an illogical reading can trick the computer into thinking the parts are swapped.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Intergas models that show the E31 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Intergas E31 fault code information on this page is sourced and cross-checked against the official Intergas service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026