What does the Ideal pressure difference < 0.9 mbar fault code mean?

Your boiler is unable to safely clear exhaust gases, which is preventing it from firing up to provide heating or hot water.

How much does it cost to fix Ideal error code pressure difference < 0.9 mbar?

Typical repair cost for the Ideal pressure difference < 0.9 mbar fault is £120-280 including labour.

Your boiler is unable to safely clear exhaust gases, which is preventing it from firing up to provide heating or hot water.

Typical repair cost for the Ideal pressure difference < 0.9 mbar fault is £120-280 including labour.

Pressure difference at switch is not greater than 0.9 mbar; check fan, pressure switch sensing pipes for blockages, bad or reversed connections.

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