6-tb Low

Worcester Bosch 6-tb Fault Code

Also written as 6TB — same fault.

The Worcester Bosch 6-tb fault code means: your boiler is currently running a self-diagnostic test to check the burner's performance across its full power range.. It appears on 1 Worcester Bosch model in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Burner test: 0...100%.

DIY fix possible

Wait for approximately 15 minutes for the test to complete automaticallyMonitor the display to see if it returns to the normal temperature readingIf the code persists for over an hour, try restarting the boiler using the reset button

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Worcester Bosch models that show the 6-tb fault code

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

Source

Worcester Bosch 6-tb 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