What does the Saunier Duval 06 fault code mean?

Your boiler has lost its ability to measure its own internal temperature correctly, so it has safely shut down to prevent overheating.

How much does it cost to fix Saunier Duval error code 06?

Typical repair cost for the Saunier Duval 06 fault is £120-180 including labour.

the heating system temperature sensor (inside the boiler) is damaged.

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Almost always a stuck diverter valve on combis.

Lockout fault with a reset-needed pattern.

Safety-critical — turn off, read this.