BoilerFaultCodesMain E154 Fault Code
The Main E154 fault code means: your boiler has noticed that water is not circulating correctly or the temperature sensors are giving conflicting readings.. It appears on 1 Main model in our database.
Technical description: Flow return sensor temperature test
What causes the Main E154 fault?
This fault occurs when the boiler's internal sensors detect that water isn't moving through the heat exchanger as quickly as it should, leading to a rapid heat build-up. The most common reasons are a failing circulation pump that can't push the water around or a blockage in the system, such as a build-up of sludge. It can also be triggered if the temperature sensors themselves have become faulty and are sending incorrect data to the control board.
This issue often comes to light during the first cold snap of autumn when the heating is turned back on after being idle all summer, which can cause internal pump parts to seize.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Main models that show the E154 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Main E154 fault code information on this page is sourced and cross-checked against the official Main service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026