Baxi 600 Combi 2 E.04.23 fault code: internal communication stoppage

The Baxi 600 Combi 2 E.04.23 fault code means “Communication internal stoppage”. That is the wording in Baxi’s current error-code table for its Combi & System 2 range.

In everyday terms, the boiler has detected that information is not moving correctly between parts of its internal control system. The boiler may stop heating water because it cannot confirm that the appliance can operate as intended. E.04.23 does not tell a homeowner which control, connection or internal component is responsible, so it should not be used to order a part or attempt a repair.

What does Baxi E.04.23 mean?

A modern boiler uses several internal controls to coordinate a heating or hot-water demand. Those controls exchange information while the appliance checks conditions, starts, runs and shuts down. E.04.23 records an interruption in that internal communication.

The word “internal” matters. This code is not the same as a wireless room thermostat losing contact with its receiver, and it is not proof that your internet connection or phone app has failed. It relates to communication inside the boiler’s controlled operating system.

The code also has limits. It does not identify a particular board, connector, cable or communication path. Different underlying faults can produce a similar interruption, and the display alone cannot separate them. A competent engineer needs to assess the appliance using the correct Baxi information for the exact model and serial details.

What might you notice at home?

Because the Baxi 600 Combi 2 supplies central heating and tap hot water from one appliance, the household effect can vary. You may notice:

• the E.04.23 code on the boiler display;
• the boiler not responding to a request for heating;
• hot taps running cold or failing to become properly hot;
• heating and hot water both becoming unavailable;
• the boiler beginning a demand and then stopping;
• a room control appearing to call for heat while the boiler remains unavailable.

These observations are useful when booking a repair, but they do not identify the failed part. Make a note of what was being requested when the code appeared, whether heating, hot water or both are affected, and whether the code is constant or intermittent.

Is E.04.23 the same on every Baxi boiler?

No. Fault-code meanings can differ between product families, even when the characters look similar. This article concerns the Baxi 600 Combi 2, which Baxi includes in the current Combi & System 2 error-code group.

Check the model name shown on the outside of the appliance or in the household paperwork before relying on this meaning. If the boiler is an older Baxi 600 Combi rather than a Baxi 600 Combi 2, use the documentation for that exact range. Give the model name and the full displayed code to the repair provider.

What can you safely check?

Keep every check outside the boiler casing. You can confirm that the household heating controls are set to request heat, note whether the boiler display is lit and check whether other obvious household electrical items appear normal. You can also look at the user-visible pressure gauge and record the reading without adjusting anything solely because E.04.23 is displayed.

If the official user guide for your exact Baxi 600 Combi 2 permits a reset, one reset can show whether the appliance returns to normal service. Follow only the user instructions for your version of the boiler. If E.04.23 remains, returns or the boiler behaves unpredictably, stop resetting it and arrange professional attention.

Do not remove the boiler case, handle internal plugs or connections, or try electrical tests. Do not enter installer settings or copy a procedure intended for a heating engineer. Repeatedly resetting the boiler can obscure an intermittent pattern without resolving the fault.

Does E.04.23 mean the boiler needs a new control board?

Not from the code alone. “Communication internal stoppage” describes what the boiler has detected, not the component that must be replaced. Assuming a particular expensive part can waste money and overlook another cause.

An engineer will use the appliance history, the way the fault presents and the manufacturer’s technical information to decide what needs attention. The useful homeowner contribution is an accurate record: the full code, the exact model, when it appeared and which services stopped working.

When should you stop using the boiler?

Leave the boiler off and seek urgent help if there is a smell of gas, a suspected carbon-monoxide alarm, scorching, smoke, unusual electrical smells, water entering electrical equipment or obvious physical damage. Do not rely on E.04.23 to judge whether a separate safety problem is present.

If you smell gas, avoid flames and electrical switches, open doors and windows if it is safe, leave the property and follow the emergency advice from the National Gas Emergency Service. If a carbon-monoxide alarm sounds or anyone has symptoms such as headache, dizziness, nausea or confusion, move into fresh air and get urgent help.

Where there is no immediate danger, E.04.23 still normally needs a professional repair because the issue concerns the boiler’s internal controls. Work involving the gas appliance should be carried out by a suitably qualified Gas Safe registered engineer.

What to tell the engineer

Have the following details ready when you book:

• the full code: E.04.23;
• the model name: Baxi 600 Combi 2;
• whether heating, hot water or both have stopped;
• whether the display stays on and whether the code is constant;
• when the problem began and whether any household power interruption happened beforehand;
• whether one guide-permitted reset changed the behaviour.

This gives the engineer a clearer picture before the visit without asking you to investigate inside the appliance.

Quick Answers

Can I keep using a Baxi 600 Combi 2 showing E.04.23?

If the boiler has stopped, will not operate normally or the code returns, arrange a repair. Stop immediately and follow emergency guidance if there is any smell of gas, carbon-monoxide alarm, smoke, scorching or electrical concern.

Will turning the boiler off and on fix E.04.23?

A single reset is reasonable only when the exact Baxi user guide permits it. If the code remains or comes back, do not continue cycling the power or repeating resets.

Is E.04.23 caused by the room thermostat?

The official meaning is an internal communication stoppage. The code does not by itself show that an external room thermostat is at fault.

Can I replace a part myself?

No. The display does not identify a part, and the relevant checks are inside a gas appliance. Keep the casing closed and use a competent Gas Safe registered engineer.