BoilerFaultCodesWorcester Bosch 1-E1 Fault Code
Also written as 1E1 — same fault.
The Worcester Bosch 1-E1 fault code means: your boiler's internal computer is reporting an error with its software version or internal memory communication.. It appears on 3 Worcester Bosch models in our database.
Technical description: Control device version: Software version of the control unit.
What causes the Worcester Bosch 1-E1 fault?
This fault occurs when the boiler's main control board loses communication with its internal memory or cannot verify its own software. It is essentially a digital handshake failure between the central processing unit and the specific data chip that tells the boiler how to operate safely. The most common reason is an electronic component failure within the printed circuit board or a corruption of the software on the code plug.
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 1-E1 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 1-E1 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