BoilerFaultCodesWorcester Bosch A3317 Fault Code
The Worcester Bosch A3317 fault code means: your boiler has detected an electrical fault with the sensor that monitors exhaust gases, causing the system to shut down for safety.. It appears on 1 Worcester Bosch model in our database.
Technical description: Short circuit in the flue gas temperature sensor contacts
What causes the Worcester Bosch A3317 fault?
This fault occurs when the electrical connection for the sensor that monitors exhaust temperatures becomes damaged or fails. The most common reasons are water ingress from heavy rain or moisture in the flue damaging the sensor's contacts, or the wiring harness becoming brittle and failing due to the high heat inside the boiler casing.
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 A3317 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch A3317 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