BoilerFaultCodesWorcester Bosch E4 Fault Code
The Worcester Bosch E4 fault code means: your boiler has detected a problem with how it controls the gas flow, meaning it cannot safely regulate the flame and has shut down as a precaution.. It appears on 2 Worcester Bosch models in our database.
Technical description: Fault with the gas modulator
What causes the Worcester Bosch E4 fault?
This fault occurs when the boiler's main control board loses the ability to vary the amount of gas entering the burner, which is necessary to maintain the correct water temperature. The most common reason is an electrical failure in the solenoid coil that moves the gas valve, or a communication error from the circuit board itself. Because the system can no longer precisely control the size of the flame, it shuts down to ensure your home remains safe.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Worcester Bosch models that show the E4 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch E4 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026