d5 Medium

Worcester Bosch d5 Fault Code

Also written as D5 — same fault.

The Worcester Bosch d5 fault code means: your boiler is struggling to accurately read the temperature of the water being sent out to your radiators because a sensor responsible for monitoring this flow has developed a fault.. It appears on 6 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: External primary NTC on low loss header defect.
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 d5 fault code

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

Source

Worcester Bosch d5 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