T.06 High

Vaillant T.06 Fault Code

Also written as T06 — same fault.

The Vaillant T.06 fault code means: your boiler is struggling to push water around your radiators because an external pump is not working as expected.. It appears on 12 Vaillant models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: External pump

What causes the Vaillant T.06 fault?

This fault occurs when the boiler detects that an additional external pump, which helps move water through your heating system, has failed or lost electrical power. The most common reason is an electrical fault in the pump itself or a break in the wiring connecting the pump to the boiler's main control board. Without this pump operating, the boiler cannot safely distribute heat, leading it to shut down to prevent overheating.

This fault is frequently seen at the start of autumn when heating systems are turned back on after months of inactivity, which can cause external pump components to seize.

Typical repair cost £180-350 (including labour)

Engineer required

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

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Vaillant models that show the T.06 fault code

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

Source

Vaillant T.06 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026