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Intergas boiler error codes

21 codes that Intergas publishes for its boilers, each with what it means, the likely cause, what you can safely check and when to call a Gas Safe registered engineer. Tap your code:

Gas boiler: do only the checks its user manual gives you — read the pressure gauge, top up through the filling loop, press the reset button, thaw a frozen condensate pipe at ground level. Keep the casing on and leave sealed parts alone. Anything else is for a Gas Safe registered engineer. If you smell gas, call the National Gas Emergency Service on 0800 111 999. Codes that need one are marked Gas Safe engineer.

Read this first

Intergas publishes the fault codes of its Xclusive and Xtreme boilers in a two-page sheet for heating engineers (version 5, 2022), which writes them as F000 to F031 under the headings fault codes and lockout codes. This page explains 21 of them. Because the sheet is written for engineers, it gives the householder no checks; we name Intergas’s own checks only so you know what the visit is about, and the one thing you can look at yourself — whether the gas to the boiler is on, for F004 — is the sheet’s first cause for that code.

F000 Heat exchanger sensor S0 defective

What it means
The temperature sensor S0 on the heat exchanger is defective.
Likely cause
A failed sensor S0.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer: Intergas’s fix is to replace the heat exchanger sensor S0.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F001 Too hot during heating

What it means
The temperature rose too high while the boiler was heating the radiators.
Likely cause
Air in the system, a pump that is not running, or the flow sensor S1 (its wiring, position or working).
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer. Intergas’s checks for them: vent the air out of the heating, check the pump (its power, a free impeller, or a new pump), then the flow sensor S1.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F002 Too hot during hot water

What it means
The temperature rose too high while the boiler was heating hot water.
Likely cause
The hot water sensor S3: its wiring, its position or the sensor itself.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer. Intergas’s checks for them: the wiring, position and working of the hot water sensor S3, then replacing it.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F003 Flue gas too hot

What it means
The flue gas temperature is too high.
Likely cause
Intergas’s check: contamination or a restriction in the heat exchanger.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer to check the heat exchanger.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F004 No flame at start-up

What it means
The burner did not light when the boiler tried to start.
Likely cause
A closed gas isolation valve or no gas supply; gas pressure at the boiler below 17 mbar (20 recommended); a blocked condensate drain or trap; the ignition module, lead or electrode; the power to the ignition module or gas valve; a poor earth.
What you can safely check

Gas boiler: do only the checks its user manual gives you — read the pressure gauge, top up through the filling loop, press the reset button, thaw a frozen condensate pipe at ground level. Keep the casing on and leave sealed parts alone.

  • Make sure the gas supply to the boiler is on — Intergas’s first cause for this code is a closed gas isolation valve or no gas supply.
When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer if the gas is on and the code stays. The rest of Intergas’s list — gas pressure, condensate trap, ignition parts, gas valve, earthing — is engineer work.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F005 Flame lost while running

What it means
The flame went out during normal operation.
Likely cause
Gas pressure at the boiler below 17 mbar; the ignition parts; the gas valve setting; flue gases being drawn back in or a blocked flue; a poor earth; a blocked condensate drain or trap.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer: every check on Intergas’s list is inside the boiler or on the gas supply.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F006 Flame simulation

What it means
The boiler detected a flame when there should be none.
Likely cause
Intergas’s check: the gas valve.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer to check or replace the gas valve.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F007 Too little ionisation current

What it means
No, or too little, ionisation current: the boiler cannot confirm its flame.
Likely cause
The ionisation/ignition electrode — its wiring, cleanliness or position.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer to check, clean or replace the ionisation and ignition electrode.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F008 Wrong fan speed

What it means
The boiler detected an incorrect fan speed.
Likely cause
The fan or its control.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer to check the fan and its wiring.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F009 Burner control fault

What it means
An internal fault in the burner control.
Likely cause
The boiler’s control electronics.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F012 Sensor S5 fault

What it means
A fault in sensor S5.
Likely cause
Sensor S5 or its wiring; Intergas’s check is the sensor’s resistance.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer to check the sensor.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F014 Heat exchanger sensor S0 mounting fault

What it means
Sensor S0 on the heat exchanger is not mounted correctly.
Likely cause
The sensor has moved or was fitted wrongly.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer to refit or check the sensor.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F015 Flow sensor S1 mounting fault

What it means
The flow temperature sensor S1 is not mounted correctly.
Likely cause
The sensor has moved or was fitted wrongly.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer to refit or check the sensor.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F016 Hot water sensor S3 mounting fault

What it means
The hot water temperature sensor S3 is not mounted correctly.
Likely cause
The sensor has moved or was fitted wrongly.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer to refit or check the sensor.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F018 Flue or air supply blocked

What it means
The flue or the air supply duct, or both, are blocked or restricted.
Likely cause
A blockage or restriction in the flue or air intake.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer to inspect the flue and air supply.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F019 Memory card (BMM) fault

What it means
A fault in the boiler’s memory card on the circuit board (BMM).
Likely cause
The circuit board’s memory module.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F027 Outside sensor S6 fault

What it means
A fault in the outside weather sensor S6.
Likely cause
The outdoor sensor or its wiring.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer or your installer to check the outdoor sensor.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F028 Reset error

What it means
A reset error; the sheet gives the name only.
Likely cause
Not stated on the sheet.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F029 Gas valve fault

What it means
A fault in the gas valve.
Likely cause
The gas valve, a sealed part.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F030 Hot water sensor S3 fault

What it means
A fault in the hot water temperature sensor S3.
Likely cause
The sensor or its wiring.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer to check the sensor.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

F031 Flow sensor S1 fault

What it means
A fault in the flow temperature sensor S1.
Likely cause
The sensor or its wiring.
What you can safely check

Nothing for the owner to check: this one is for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer
Gas Safe engineer Call a Gas Safe registered engineer to check the sensor.

Source: Intergas, Xclusive and Xtreme boiler range: parameters, fault codes and lockout codes for engineers (V5, 2022) Checked 2026-09-29.

A code that is not listed here

The sheet also prints F010 and F011 as sensor faults, but we could not read which sensor each refers to, so they are left out rather than guessed. Older Intergas boilers such as the Combi Compact HRE use short numbers instead, explained in their own operating instructions. For any code not here, ask a Gas Safe registered engineer or Intergas.

We list only codes the source below states. If your code is not here, it may belong to a model the source does not cover: your model’s manual is the authority.

Related pages

Source

Every code on this page comes from this page, published by Intergas and read on the date shown. Meanings are written in our own words; nothing is taken from other makes, other models or third-party code sites.