Worcester Bosch CE 266 Fault Code: Causes, Fixes & Repair Costs
What does the Worcester Bosch CE 266 fault code mean?
The CE 266 code appears on Worcester Bosch boilers when the control system has detected an abnormality with the central heating circulation pump. This could mean the pump has stopped running, is running erratically, or there is a communication problem between the pump and the PCB. The boiler will typically block or lock out to prevent overheating and component damage. The CE prefix on Worcester Bosch boilers generally relates to the sealed heating circuit and circulation — other CE codes such as CE 207 relate to low system pressure, while CE 266 specifically points to a pump-level fault. Because this code can involve both mechanical pump issues and electrical/PCB communication faults, a Gas Safe registered engineer with Worcester Bosch diagnostic equipment is required to properly investigate and resolve it.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. 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.
Common causes
- Seized or sticking circulation pump Common
Over time, especially in systems with sludge or limescale build-up, the pump impeller can seize up or stick. The boiler's control board detects that flow is not occurring as expected and triggers the CE 266 lockout. This is the most common root cause and is often accompanied by gurgling or humming sounds from the pump.
- Airlock in the pump or heating circuit Common
An air pocket trapped inside the pump or pipework can prevent adequate water circulation. The pump may spin but move little or no water, causing the boiler to detect a circulation fault. Low system pressure can make airlocks more likely to form.
- Low system pressure reducing pump effectiveness Common
If the system pressure has dropped below around 1 bar, there may be insufficient water in the circuit for the pump to circulate effectively. While low pressure alone may trigger a different CE code, it can also contribute to pump-related faults by starving the pump of water.
- Sludge or limescale blocking circulation Sometimes
Magnetite sludge or limescale deposits in the pipework or heat exchanger can restrict flow to the point where the pump cannot maintain adequate circulation. The boiler interprets this restriction as a pump fault and shuts down to prevent overheating.
- PCB communication fault with the pump Sometimes
The pump on modern Worcester Bosch boilers communicates with the PCB electronically. A wiring fault, loose connection, or a failing PCB can cause the board to report a pump error even if the pump itself is mechanically sound.
- Pump overheating or internal failure Rare
The pump motor may have suffered internal electrical failure or overheating due to prolonged poor circulation. In this case the pump will need replacing rather than simply freeing or bleeding.
How to fix it
- Check your system pressure gauge DIY safe
Look at the pressure gauge on the front of the boiler. It should read between 1.0 and 1.5 bar when the system is cold. If it has dropped below 1 bar, top it up using the filling loop (usually a braided hose or lever beneath the boiler) until the gauge returns to around 1.2–1.5 bar, then close the filling loop fully. Low pressure alone can contribute to circulation problems.
- Bleed your radiators to release trapped air DIY safe
Turn off the boiler and allow the system to cool slightly. Use a radiator bleed key to open the bleed valve on each radiator (typically at the top corner) until water dribbles out steadily and no air hisses. Re-check and re-pressurise after bleeding as releasing air can cause a small pressure drop.
- Reset the boiler once DIY safe
Press and hold the reset button (or turn the temperature dial to the reset position and hold for approximately 3 seconds, depending on your model). Attempt a single reset only. If the CE 266 code returns immediately or after a very short time, do not keep resetting — repeated resets without resolving the underlying fault can mask a more serious problem and may cause further damage.
- Check that the gas supply is on and other gas appliances work DIY safe
Confirm your gas supply is functioning normally by checking that a gas hob or other appliance works. If you have no gas supply, contact your gas supplier rather than continuing to reset the boiler.
- Call a Gas Safe registered engineer to diagnose and repair the pump fault Gas Safe engineer
If the fault persists after the checks above, a qualified Gas Safe registered engineer needs to attend. They will open the boiler casing, inspect the pump for seizure, blockage, or electrical failure, test wiring and connections between the pump and PCB, and use Worcester Bosch diagnostic tools if needed. They may free or replace the pump, repair wiring, replace the PCB, or recommend a powerflush if system sludge is found to be the underlying cause. Do not attempt to open the boiler casing or touch internal components yourself.
Parts you may need
- Central heating circulation pump (Worcester Bosch compatible) · from £120
- Pump wiring harness / connector loom · from £25
- PCB (printed circuit board) · from £200
- Magnetic system filter (e.g. Magnaclean) · from £75
- Inhibitor and system cleaner fluid · from £20
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 £150–£380, depending on the underlying cause.
Frequently asked questions
Can I fix a CE 266 fault myself without calling an engineer?
Only to a limited extent. You can safely check and top up the system pressure, bleed radiators to clear airlocks, and attempt a single boiler reset. However, investigating or replacing the circulation pump, testing PCB connections, or opening the boiler casing must only be done by a Gas Safe registered engineer. Attempting internal repairs yourself is dangerous and will likely invalidate your boiler warranty.
How much does it cost to fix a Worcester Bosch CE 266 fault?
Most homeowners pay between £150 and £380 to resolve a CE 266 fault. Freeing a seized pump or clearing an airlock at the lower end, a full pump replacement typically costs £150–£300 including parts and labour, and a PCB repair or replacement can add £150–£250 on top if that component is also at fault. If a powerflush is recommended to clear system sludge, this is typically an additional £300–£600 depending on the size of the system. Note that labour rates in London and the South East tend to be higher than the rest of the UK.
What is the difference between CE 266 and CE 207 on a Worcester Bosch boiler?
CE 207 is a low system pressure fault — the boiler has detected that the water pressure in the sealed heating circuit has dropped too low, often below 0.5 bar. This is frequently something a homeowner can resolve by topping up pressure via the filling loop. CE 266, by contrast, is a pump fault: the boiler's control system has detected a problem with the circulation pump itself, which requires a Gas Safe engineer to investigate properly. The two codes can be related — chronically low pressure can contribute to pump problems — but CE 266 goes beyond a simple pressure issue.
My Worcester Bosch boiler is over 10 years old and keeps showing CE 266 — should I repair or replace it?
If your boiler is over 10–12 years old and is repeatedly triggering CE 266 or other fault codes, it is worth comparing the repair cost against a new boiler. A pump replacement on an ageing boiler may be a short-term fix if other components are also wearing out. A new Worcester Bosch boiler typically comes with a manufacturer warranty of 8–12 years (depending on installer accreditation), which would cover future pump and part faults. Ask your engineer for an honest assessment of the boiler's overall condition before committing to an expensive repair.