Worcester Bosch 1010 Fault Code: Causes, Fixes & Repair Costs
What does the Worcester Bosch 1010 fault code mean?
The 1010 fault code (often displayed as '1010 O' on the boiler display) indicates that the boiler's EMS-Bus (Energy Management System Bus) has lost communication. The EMS-Bus is an internal data network that links the boiler's control board with other components and external controls. When this communication link breaks down — whether due to a disconnected cable, physical damage, or a blown fuse — the boiler shuts itself down as a precaution and displays this code. Unlike some fault codes that have numeric sub-variants, 1010/1010 O refers specifically to an absent or non-functioning BUS communication cable rather than a range of sensor failures, so the diagnostic path is relatively focused.
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.
Common causes
- Disconnected or loose EMS-Bus cable Common
The most frequent cause. The EMS-Bus cable may have worked loose from its connector on the PCB or an intermediate connection point — sometimes during a previous service or if the boiler has experienced vibration over time. A loose connection interrupts the data signal and triggers the fault.
- Physically damaged EMS-Bus cable Sometimes
The cable itself may have been pinched, frayed, cut, or degraded over time, particularly if it runs near sharp metalwork inside the boiler casing. Even minor damage to the insulation or internal conductors can corrupt the communication signal enough to cause a lockout.
- Blown internal fuse on the EMS-Bus circuit Sometimes
A short circuit or voltage spike can blow the fuse that protects the EMS-Bus circuit. The cable may appear intact, but the fuse failure means no signal can pass. This tends to be less obvious and requires an engineer to test and confirm before replacing.
- PCB fault or damage Rare
If the EMS-Bus cable and fuse both check out, the fault may lie with the PCB itself — either a failed communication chip or wider PCB damage. This is the least common cause but the most expensive to resolve.
How to fix it
- Reset the boiler once DIY safe
Press and hold the reset button (typically the flame symbol with a line through it) for around 3 seconds, then wait for the boiler to restart. If the 1010 code reappears immediately or after a short while, a reset alone will not resolve the underlying fault. Do not reset more than 2–3 times in total.
- Check that your gas supply is working DIY safe
Confirm that other gas appliances in your home (such as a gas hob) are functioning normally. If you have no gas supply, contact your gas network provider rather than an engineer. If gas is available, the issue is internal to the boiler.
- Do not open the boiler casing or touch any internal wiring Gas Safe engineer
The EMS-Bus cable and all associated connections are inside the boiler casing. Opening the casing yourself is unsafe, can invalidate your warranty, and in some circumstances may breach building regulations. Leave all internal inspection to a qualified engineer.
- A Gas Safe engineer inspects and reseats the EMS-Bus cable connections Gas Safe engineer
The engineer will open the casing safely, locate the EMS-Bus cable connectors at the PCB and any intermediate terminals, and check that every connection is fully seated. A loose plug is often all that needs correcting, making this one of the quicker and less expensive resolutions.
- Engineer checks the cable for physical damage and replaces if necessary Gas Safe engineer
The cable is inspected along its full length for cuts, fraying, pinch points, or heat damage. If damaged, a replacement cable is fitted. This is a straightforward repair when the correct cable is available, and labour time is usually under an hour.
- Engineer tests and replaces the EMS-Bus circuit fuse if blown Gas Safe engineer
Using a multimeter, the engineer tests the relevant fuse. If it has blown, the underlying cause of the short is identified first before a replacement fuse is installed — simply replacing a fuse without finding the root cause risks it blowing again.
- Engineer assesses the PCB if the above steps do not resolve the fault Gas Safe engineer
If the cable, connectors, and fuse are all in order but the 1010 fault persists, the PCB is likely at fault. The engineer will advise on repair versus replacement. PCB replacement is the most expensive outcome and may prompt a conversation about whether boiler replacement is more cost-effective on an older unit.
- Call a Gas Safe registered engineer if you have not already done so Gas Safe engineer
Because every corrective step for the 1010 code involves work inside the boiler casing, a Gas Safe registered engineer is required from the outset. You can verify an engineer's registration at gassaferegister.co.uk. Always request a written quote before work begins.
Parts you may need
- EMS-Bus communication cable · from £35
- EMS-Bus circuit fuse (boiler-specific) · from £8
- Worcester Bosch PCB (model-dependent) · 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 £100–£300, depending on the underlying cause.
Frequently asked questions
Can I fix a Worcester Bosch 1010 fault myself?
No. While you can safely attempt a single reset, every other step — reconnecting the cable, inspecting for damage, testing the fuse, or assessing the PCB — requires access to the inside of the boiler casing. This must only be carried out by a Gas Safe registered engineer. Attempting it yourself is dangerous and will almost certainly void your boiler warranty.
How much does it cost to fix a Worcester Bosch 1010 fault code in the UK?
For the most common fixes — reseating a loose cable or replacing a damaged EMS-Bus cable — most homeowners pay between £100 and £300 including call-out and labour. If a fuse replacement is all that is needed, the cost sits towards the lower end. A PCB replacement is a less likely outcome but considerably more expensive, typically £400–£650 depending on the boiler model and your location. If an engineer quotes for PCB work on a boiler over 10 years old, it is worth asking for a comparison quote on a new boiler at the same time.
Why does my Worcester Bosch show '1010 O' rather than just '1010'?
The 'O' suffix stands for 'open' or 'offline', indicating that the EMS-Bus connection is not present or not responding. It is the same underlying fault as 1010 — an absent or broken BUS communication link — and the diagnostic and repair process is identical. You may see either display depending on your boiler model's firmware version.
Will an annual boiler service help prevent the 1010 fault code?
Yes, to a degree. During a service, an engineer checks internal connections and cable condition, which means a loose EMS-Bus connector is likely to be spotted and corrected before it causes a breakdown. A UK boiler service typically costs £90–£120 and is the single most effective way to catch developing faults early. It also keeps your warranty valid on models that require annual servicing.