BoilerFaultCodesWorcester Bosch 1-E4 Fault Code
Also written as 1E4 — same fault.
The Worcester Bosch 1-E4 fault code means: your boiler has detected an internal software conflict or an incorrect configuration chip, preventing it from operating correctly.. It appears on 3 Worcester Bosch models in our database.
Technical description: Code plug version: Coding plug version.
What causes the Worcester Bosch 1-E4 fault?
This fault occurs when the boiler's main control board cannot communicate correctly with the small electronic chip that tells it which specific model it is. The most common reason is that the coding plug has become loose, damaged, or is incompatible with the circuit board, leading the system to shut down for safety. In some cases, this happens following a power surge or if the internal memory on the main board has failed.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Worcester Bosch models that show the 1-E4 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 1-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