If your Worcester Bosch Greenstar boiler is showing a 1010 O error code, it means the system has lost communication between its components — no bus communication. It's a common fault, and it nearly always comes down to the EMS-Bus cable.
What the 1010 O error code means
The 1010 O code points to one thing: the boiler can't talk to its own parts. Two readings sit behind it:
- No bus communication cable?
- The EMS-Bus isn't connected, or it's damaged
When that link breaks, the boiler can't run properly. Nine times out of ten it's a loose or damaged EMS-Bus cable. If you're seeing a different code instead, our guide to Worcester Bosch fault codes covers the rest.
What causes the 1010 O fault
A faulty BUS communication cable is behind almost every 1010 O fault. Without that connection, the boiler's components can't share information, so the system won't run. Two causes are common.
EMS-Bus not connected or damaged
If the EMS-Bus cable is loose at a connection or physically damaged, communication between the boiler's parts is cut off.
Damaged cable or blown fuse
A damaged cable stops signals passing through the BUS communication line. A blown fuse can trigger the same code.
How to fix the 1010 O error code
This isn't a DIY fix. The 1010 O fault sits inside the boiler's wiring and electrics, so it needs a Gas Safe registered engineer. Here's what they'll check.
Check the EMS-Bus connection
First, the engineer checks the EMS-Bus cable is plugged in securely. A loose or half-seated connection is enough to drop communication and throw the code.
Check the cable integrity
Next, they inspect the cable itself for cuts, fraying or wear. A damaged cable causes transmission errors, and if it's beyond repair they'll renew it.
Replace the fuse
If the cable checks out, the engineer looks at the relevant fuse. A blown fuse can cause the same communication failure, and it still takes a qualified engineer to replace it safely.
Get a Worcester Bosch engineer out
Some boiler faults look worse than they are — but a 1010 O still needs sorting quickly before it leaves you without heating or hot water. At Serviceteam in London, our engineers are Worcester Bosch-accredited and Gas Safe registered, so they can legally handle any boiler repair in London, from a 1010 O fault to a full breakdown. We're available 24/7 for emergencies.
Got a 1010 O fault on your Worcester Bosch? Book a boiler repair online — we'll get a Gas Safe engineer out to you fast, day or night.
