375 / E4 Medium

Worcester Bosch 375 / E4 Fault Code

Also written as 375E4 — same fault.

The Worcester Bosch 375 / E4 fault code means: your boiler is having trouble reading the temperature of the incoming cold water, which may cause your hot water to fluctuate in temperature or not heat up correctly.. It appears on 2 Worcester Bosch models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Preheat sensor on DHW inlet Short Circuit
Typical repair cost £120-220 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Worcester Bosch models that show the 375 / E4 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch 375 / 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