Atag Fault Code 119: Link on X2 Position 4 and 5 Missing
Fault code 119 on Atag boilers indicates that the control board (PCB) cannot detect the required link — sometimes called a jumper — across positions 4 and 5 of the X2 connector. This link tells the boiler how it is configured, and without it the boiler locks out completely, displaying a bell symbol on the screen. The fault is purely electrical/electronic in nature and has nothing to do with the gas circuit, but it does require an engineer to resolve safely.
General guidance only — not a substitute for professional advice. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
What does the ATAG 119 fault code mean?
Fault code 119 on Atag boilers indicates that the control board (PCB) cannot detect the required link — sometimes called a jumper — across positions 4 and 5 of the X2 connector. This link tells the boiler how it is configured, and without it the boiler locks out completely, displaying a bell symbol on the screen. The fault is purely electrical/electronic in nature and has nothing to do with the gas circuit, but it does require an engineer to resolve safely.
Common causes
- Dislodged or missing X2 jumper link Common
The most frequent cause. The small jumper link bridging positions 4 and 5 on the X2 connector can be knocked loose during a service visit or routine maintenance. If the engineer did not notice it had shifted or fallen off, the boiler will lock out on the next startup.
- Loose or disconnected X2 wiring harness Common
The plug-in connector that houses the link can work itself loose over time due to vibration. Even if the link itself is present, a poorly seated connector will prevent the PCB from reading it, triggering the same fault.
- Corroded or damaged connector contacts Sometimes
Moisture inside the boiler casing — for example from a minor internal leak or condensation — can corrode the metal contacts on the X2 connector. Damaged or pitted contacts may break the circuit even when the link is physically present.
- Incorrect commissioning or installation configuration Sometimes
On a newly installed or recently replaced boiler, if the engineer did not fit the X2 link correctly during commissioning, fault 119 will appear at first start-up.
- Faulty PCB Rare
In rare cases where the connector and link are confirmed to be in good condition, the PCB itself may have developed a fault on the circuit that reads the X2 link, making it appear absent to the board's firmware.
How to fix it
- Try resetting the boiler once DIY safe
Press and hold the reset button (usually marked with a flame or reset symbol) for a few seconds until the boiler attempts to restart. A one-off lock-out can occasionally be cleared by a reset, but if the X2 link is genuinely missing or loose this will not resolve the underlying problem. Do not reset more than two or three times — repeated unsuccessful resets can mask the fault and cause wear on components.
- Check that the boiler's gas supply is on DIY safe
Although fault 119 is a wiring fault rather than a gas supply fault, it is worth confirming that your gas meter isolation valve is open and that other gas appliances in the property (hob, gas fire) are working normally. If there is a wider gas supply issue, call your gas supplier before doing anything else.
- Do not attempt to open the boiler casing or inspect the PCB yourself Gas Safe engineer
The X2 connector is located on the internal PCB inside the boiler casing. Accessing it requires removing the boiler cover and working in close proximity to electrical components and gas pipework. This must only be done by a Gas Safe registered engineer. Attempting it yourself is dangerous and will likely void any remaining warranty.
- Engineer to inspect the X2 connector and jumper link Gas Safe engineer
A Gas Safe engineer will power the boiler down safely, remove the casing, and locate the X2 connector on the PCB. They will check whether the jumper link is present, seated correctly, and making proper contact at positions 4 and 5. If the link is simply dislodged it can be repositioned in a matter of minutes.
- Engineer to check the full X2 wiring harness for damage or corrosion Gas Safe engineer
If the link is present and seated correctly, the engineer will inspect the individual wires running into the X2 plug. They will look for broken insulation, corroded pins, or intermittent connections that could prevent the PCB from reading the link correctly. Damaged sections of harness will need to be repaired or replaced.
- Engineer to reset and test the boiler after remedial work Gas Safe engineer
Once the connector has been inspected and corrected, the engineer will refit the casing, restore power, reset the boiler, and run it through a full heat and hot-water cycle to confirm fault 119 has cleared and the boiler is operating safely.
- PCB replacement if the fault persists Gas Safe engineer
If the connector and link are in perfect condition but the fault still appears, the PCB itself is likely faulty and will need replacing. Only a Gas Safe engineer should source and fit a replacement board, as incorrect fitting can create a dangerous situation.
- Call a Gas Safe registered engineer if you have not already done so Gas Safe engineer
Fault 119 cannot be resolved through any homeowner action beyond a single reset attempt. Book a Gas Safe registered engineer to diagnose and repair the fault. You can verify an engineer's registration at www.gassaferegister.co.uk.
Parts you may need
- X2 PCB jumper/link connector · from £8
- Boiler wiring harness (X2 section) · from £45
- Replacement PCB (Atag iC/iS/iR series) · from £280
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £120–£350, depending on the underlying cause.
Frequently asked questions
Is Atag fault code 119 the same as a fan fault?
No. Some third-party websites incorrectly describe code 119 as a fan error. According to the official Atag iC, iS, and iR series manuals, fault 119 specifically means the link on the X2 connector at positions 4 and 5 is missing or undetected. The fan fault on Atag boilers is a different code entirely (code 129). Always check the official documentation rather than relying on generic fault-code lists.
Can I fix Atag fault 119 myself?
Not safely, no. The fix involves accessing the PCB inside the boiler casing, which requires working near electrical components and gas pipework. This is work for a Gas Safe registered engineer. The only action a homeowner should take is a single boiler reset to see if the fault clears on its own — if it does not, call an engineer.
How much will it cost to fix fault code 119 on my Atag boiler?
If the X2 jumper link simply needs reseating or replacing, you are typically looking at a call-out charge plus a small amount of labour — expect to pay somewhere in the region of £120–£200 in total. If the wiring harness is damaged, costs may rise to around £200–£350 once parts and labour are included. In the relatively uncommon situation where the PCB itself has failed and needs replacing, the total bill including parts and labour could reach £400–£600 or more, depending on your location and the engineer's rates.
Will my boiler produce any heat or hot water while showing fault 119?
No. Fault 119 causes a full boiler lock-out, indicated by a bell symbol on the display. The boiler will not fire for either central heating or domestic hot water until the fault is resolved and the boiler is successfully reset. If you have vulnerable people in the household or the weather is very cold, treat this as a priority repair.