Worcester Bosch CE Fault Code: Causes, Fixes & Repair Costs
What does the Worcester Bosch CE fault code mean?
The CE fault code on a Worcester Bosch boiler most commonly signals that the system water pressure has dropped below the safe operating threshold — typically under 0.7 bar. A healthy sealed heating system should sit between 1.0 and 1.5 bar when cold. On certain Worcester Bosch models the display shows a numeric sub-code alongside CE, and these point to temperature or flow sensor faults rather than a pressure issue. The three main sub-codes to know are: CE 201 (flow temperature sensor fault — the sensor or its wiring is giving an incorrect or no reading), CE 203 (flow sensor fault — the sensor monitoring water flow through the primary circuit has failed or is misreading), and CE 207 (a broader sensor fault where one of the boiler's temperature sensors is reporting outside its expected range). If your display simply shows CE or CE 207 without any history of sensor work, start by checking system pressure before assuming the worst.
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
- Low system pressure (gradual loss over time) Common
Sealed heating systems naturally lose a small amount of pressure over months and years. If your gauge reads below 1 bar and the boiler has not been touched recently, a straightforward top-up via the filling loop is usually all that is needed. This is the single most common reason a CE code appears.
- Pressure drop after bleeding radiators Common
Bleeding trapped air from radiators releases water vapour and reduces circuit pressure. If you have recently bled one or more radiators and the CE code appeared shortly afterwards, low pressure is almost certainly the cause.
- Faulty or weeping pressure relief valve (PRV) Sometimes
The PRV is designed to open and discharge water if pressure gets too high. Over time the valve seat can deteriorate and allow a slow, continuous drip — enough to steadily reduce system pressure without an obvious puddle. Check whether the external discharge pipe from the PRV has any signs of dripping or lime scale staining.
- Leak in the heating circuit Sometimes
A pinhole leak on a pipe joint, radiator valve, or pump seal can cause repeated pressure loss. If you find yourself topping the system up more than once every few weeks, a hidden leak is the likely culprit. Constant fresh-water top-ups also introduce oxygen that accelerates internal corrosion.
- Failing expansion vessel Sometimes
The expansion vessel absorbs pressure changes as water heats and cools. If the internal diaphragm ruptures, the vessel can no longer do its job and pressure swings become erratic, sometimes triggering a CE code even when no water has been lost.
- Flow temperature sensor fault (CE 201 / CE 203) Sometimes
The sensors that monitor primary flow temperature can fail due to damaged wiring, corroded connections, moisture ingress, or the sensor body itself degrading. When the boiler cannot get a reliable temperature reading it shuts down to prevent overheating damage.
- Sensor wiring or PCB connection issue (CE 207) Rare
Loose connector pins, chafed wiring, or a corroded plug on the sensor loom can cause intermittent or permanent CE 207 faults even when the sensor itself is perfectly serviceable. An engineer will test the circuit before condemning the sensor.
How to fix it
- Check the pressure gauge on the boiler DIY safe
Look at the pressure gauge on the front of the boiler (or in the app if you have a connected model). If it reads below 1 bar — or is in the red zone — low pressure is the likely cause of the CE code. If the gauge reads between 1 and 1.5 bar, the fault is more likely sensor-related (CE 201, CE 203, or CE 207) and you should skip to step 5.
- Top up system pressure using the filling loop DIY safe
Locate the filling loop — usually a silver or grey braided hose with one or two valves beneath the boiler. Slowly open the valve(s) and watch the gauge rise. Stop when it reaches 1.2–1.5 bar. Close the valve(s) fully. Never overfill above 2 bar. Consult your boiler manual if you are unsure which type of filling loop your model has.
- Reset the boiler DIY safe
Once pressure is restored, press and hold the reset button (usually marked with a flame or restart symbol) for around 3 seconds, or follow the reset procedure in your model's handbook. Allow the boiler a couple of minutes to restart and run through its ignition sequence. Do not reset more than 2–3 times in total.
- Monitor pressure over the following days DIY safe
If the pressure holds steady and the CE code does not return, the issue was simply low pressure — no further action is needed. If the pressure drops again within a week or two, stop topping up and call an engineer. Repeatedly repressurising masks an underlying leak and accelerates internal corrosion.
- If the pressure was normal or the CE code returns, call a Gas Safe registered engineer Gas Safe engineer
A persistent CE code alongside normal pressure almost certainly points to a sensor fault (CE 201, CE 203, or CE 207). An engineer will test the flow temperature sensor, inspect wiring harnesses and connector pins, check sensor positioning in the pocket, and replace any faulty components. They will also carry out a leak-down test if pressure loss is recurring, inspect the PRV, and check the expansion vessel charge pressure — none of which are safe or appropriate for a homeowner to attempt.
Parts you may need
- Flow temperature sensor (NTC thermistor) · from £25
- Pressure relief valve (PRV) · from £35
- Expansion vessel diaphragm / replacement vessel · from £55
- Sensor wiring loom / connector harness · from £30
- Filling loop assembly · 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 £120–£380, depending on the underlying cause.
Frequently asked questions
Can I fix a CE fault code myself?
If the CE code is caused by low pressure, yes — topping up via the filling loop is a straightforward DIY task and costs nothing. However, if the pressure drops repeatedly, or if your display shows CE 201, CE 203, or CE 207, you will need a Gas Safe registered engineer. Sensor replacements, leak repairs, PRV work, and expansion vessel servicing all require a qualified professional.
What is the difference between CE 201, CE 203, and CE 207?
All three relate to temperature or flow sensing but point to slightly different circuits. CE 201 indicates a fault with the primary flow temperature sensor or its wiring. CE 203 suggests the flow sensor (which measures water movement through the circuit) has failed or is misreading. CE 207 is a broader sensor fault that can apply to more than one sensor on the boiler. In practice, an engineer will use diagnostic equipment to pinpoint exactly which sensor or connection is at fault regardless of the sub-code shown.
How much does it cost to fix a Worcester Bosch CE fault in the UK?
If the cause is simply low pressure, the only cost is your time — the fill is free. If you need an engineer to diagnose and repressurise the system, expect to pay roughly £80–£120 for the call-out. A sensor replacement (parts and labour) typically costs £150–£350. Leak repairs vary depending on location and accessibility, usually falling in the £150–£400 range. PRV and expansion vessel work generally sits between £150 and £300. In rare cases where the fault has damaged the PCB or heat exchanger, costs can be significantly higher — an engineer can advise whether repair or replacement is the better value.
Why does my boiler keep losing pressure and showing CE?
Repeated pressure loss nearly always means there is a leak somewhere in the system — even if you cannot see an obvious drip. Common culprits include weeping radiator valves, a slowly discharging PRV, a leaking pump seal, or corroded pipe joints hidden behind walls or under floors. A failed expansion vessel diaphragm can also cause the pressure gauge to fluctuate unusually. Every time you top the system up you introduce fresh oxygenated water, which speeds up internal corrosion. If you have repressurised more than once in the past month, stop topping up and book a Gas Safe engineer to find and fix the source.