Worcester Bosch CC Fault Code: Causes, Fixes & Repair Costs
What does the Worcester Bosch CC fault code mean?
The CC fault code on a Worcester Bosch boiler signals a problem with the outdoor temperature sensor — specifically an open or short circuit in the sensor or its wiring. The outdoor sensor feeds live temperature data to the boiler so it can adjust its output intelligently through weather compensation. When this communication breaks down, the boiler detects the fault and displays CC alongside the flashing fault indicator LED. In most cases the boiler will carry on heating your home, but weather compensation will no longer function correctly, meaning the system cannot fine-tune itself to outdoor conditions and may run less efficiently than usual. This fault only applies to installations where an outdoor sensor has actually been fitted — if no sensor is connected, the code will not appear.
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
- Outdoor sensor failure or wear Common
The sensor itself has degraded or failed outright, sending an incorrect signal — or no signal at all — back to the boiler's control system. This is the single most common reason the CC code appears and is usually resolved by fitting a replacement sensor.
- Wiring open or short circuit Common
The cable running from the outdoor sensor to the boiler can develop a break or a short, especially if it runs along an exposed external wall or through areas prone to rodent activity or building work. The boiler's PCB interprets either condition as a sensor fault.
- Water ingress or physical damage to the sensor Sometimes
Outdoor sensors are mounted externally and are therefore exposed to the elements. Heavy rain, condensation pooling inside the sensor housing, or accidental knocks during garden work or building maintenance can all cause the unit to malfunction or lose its wiring connection.
- Faulty PCB (control board) Rare
In a small number of cases the PCB itself is unable to read the sensor signal correctly even when the sensor and wiring are intact. This is a less common root cause but should be investigated by an engineer once the sensor and wiring have been ruled out.
How to fix it
- Reset the boiler DIY safe
Press and hold the reset button on your boiler for around three seconds until the display responds. On models with a rotary dial, turn it to the reset position and hold briefly. If the CC code clears and stays clear, the fault may have been a temporary glitch. Limit resets to two or three attempts — repeated resets without a lasting fix will not solve an underlying component fault.
- Visually check the outdoor sensor for obvious damage DIY safe
Go outside and take a look at the sensor, which is typically a small plastic unit fixed to an external wall. Check whether it has been knocked out of position, whether the cable appears cut or crushed, and whether the sensor housing looks cracked or waterlogged. Do not attempt to open, test, or disconnect the sensor yourself — just note what you can see and report it to your engineer.
- Have a Gas Safe engineer test the sensor and wiring Gas Safe engineer
A registered engineer will use a multimeter to check the sensor's resistance value against the manufacturer's specification and trace the wiring for any open or short circuit. This confirms whether the sensor, the cable, or the connection at the PCB is at fault before any parts are ordered.
- Sensor replacement if confirmed faulty Gas Safe engineer
If testing points to a failed sensor, the engineer will fit a compatible replacement outdoor temperature sensor and verify the weather compensation function is restored before leaving. This is the most common fix for the CC code and is usually straightforward.
- PCB investigation if sensor and wiring are sound Gas Safe engineer
Should the sensor and its wiring test correctly, the engineer will assess the PCB for signs of damage or failure. PCB replacement is a more involved repair and carries a higher cost, but it is the logical next step when all other components check out.
- Call a Gas Safe registered engineer if you cannot resolve the fault Gas Safe engineer
If the boiler continues to display CC after your visual checks and a reset or two, book a Gas Safe registered engineer to carry out a proper diagnosis. You can verify an engineer's registration at gassaferegister.co.uk before they visit.
Parts you may need
- Worcester Bosch outdoor temperature sensor · from £35
- Sensor extension/connection cable · from £15
- Worcester Bosch PCB (control board) · from £220
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–£280, depending on the underlying cause.
Frequently asked questions
Will my boiler still heat my home while the CC fault code is showing?
In most cases, yes. The CC code is a warning rather than a full lockout, so the boiler typically continues to fire and provide heating and hot water. What you lose is weather compensation — the boiler can no longer adjust its output based on outdoor temperature, so it may run less efficiently or feel slightly less responsive. That said, if the boiler also trips out on a separate fault, or if you have reset it multiple times without success, stop resetting and call an engineer.
Can I replace the outdoor temperature sensor myself to fix the CC code?
Although the sensor itself is not a gas component, sensor replacement on a Worcester Bosch boiler still requires correct diagnostic testing with a multimeter to confirm the part is actually at fault — fitting a new sensor without testing first can waste money if the real problem lies in the wiring or the PCB. A Gas Safe registered engineer is best placed to test, confirm, and replace the component correctly, and the job is typically quick and affordable.
How much does it cost to fix a Worcester Bosch CC fault code in the UK?
For the majority of homeowners, fixing a CC fault code means replacing the outdoor temperature sensor, and the total cost including call-out, labour, and parts usually falls in the region of £120–£280 depending on your location and the engineer's rates. If the underlying cause turns out to be a faulty PCB rather than the sensor itself, costs can rise considerably — PCB replacement typically adds £200–£350 on top of labour — but this scenario is much less common.
My outdoor sensor looks fine from the outside — could the wiring be the real problem?
Absolutely. A sensor that looks undamaged can still be connected via a cable that has developed an internal break or a short circuit along its length, particularly where it passes through walls or runs along external surfaces exposed to frost and damp. Your engineer will test the full circuit — sensor resistance plus continuity of the cable — to pinpoint exactly where the fault lies before recommending any parts.