What E04 and E.04.10 mean
E.04.10 is an ignition lockout. Your Baxi tried to light the burner several times, never detected a flame and shut itself down. Sometimes the cause is outside the boiler, such as a gas supply problem, but if gas is reaching the boiler it is an internal fault for a Gas Safe registered engineer.
Baxi's newer boilers use a three-part code. The letter E marks an error, the 04 is the fault group and the number after the second dot identifies the exact fault. The Combi 2/2.1 installation and service manual (7875578-02) lists the E.04 family as permanent faults, and the 600 Combi 2 manual heads the same table "permanent faults that require resetting". Unlike a temporary fault, the boiler will not try again by itself. It stays locked out until someone presses reset.
If you have a room unit or controller connected, it may show 254 rather than the boiler's code. Both the 400 Combi 2.1 and 600 Combi 2 manuals say to read the code on the boiler's own display.
Which Baxi boilers show E.04.10
| Boiler | Document | Wording for E.04.10 |
|---|---|---|
| 400 Combi 2.1, 600 Combi 2, 800 Combi 2, Assure 500 Combi 2 | Installation and Service Manual, Combi 2/2.1 (7875578-02), p.53 | "Burner failed to ignite after 4 attempts" |
| 600 Combi 2 24, 30 and 36 | Installation and Service Manual, section 11, pp.76 to 77 | "Burner failed to ignite after 4 attempts" |
| 200 Combi (224, 228) and 400 Combi (424, 428, LPG) | Installation and Service Manual 7696317, pp.65 to 69 | "5 burner start-up failures" (shown as E:04.10) |
Older Baxi boilers report a comparable situation as E133, "interruption of gas supply or flame failure", so our Baxi E133 page is the one to read if your boiler uses the older E codes.
Other E04 codes you might see
E04 on its own does not tell you much. The two digits after it matter, and the manuals list several:
| Code | Baxi description |
|---|---|
| E.04.01 | Flow temperature sensor short circuited |
| E.04.02 | Flow temperature sensor disconnected |
| E.04.08 | Maximum safe temperature value reached |
| E.04.10 | Burner failed to ignite after 4 attempts |
| E.04.12 | Ignition failure, flame monitoring (false flame signal on the 200/400 Combi) |
| E.04.13 | Fan impeller blocked or maximum rpm exceeded |
| E.04.15 | Flue gas exhaust pipe blocked (600 Combi 2) |
| E.04.17 | Fault in gas valve control circuit |
Why the burner fails to light
The manuals give engineers a list of things to check for the ignition faults. They fall into a few groups:
- Gas supply. Gas supply pressure, and whether the gas valve is fully open. The 200/400 Combi manual also says to purge the gas supply to remove air, which is relevant after a new meter or work on the gas pipes.
- Gas valve. Its electrical connection, calibration and operation.
- Ignition. The electrode's condition and connections, and on the 200/400 Combi the cabling of the ignition transformer.
- Other checks. Fan operation, flue blockages, the earth circuit and the supply voltage are also listed alongside the ignition codes.
Safe checks before you reset
- Test another gas appliance. If the hob will not light either, the problem is the supply, not the boiler.
- Check the meter. Make sure a prepayment meter has credit and the emergency control lever at the meter is on.
- Check the isolation valve. The gas valve on the pipe under the boiler should have its handle in line with the pipe. If it is across the pipe, it is closed.
- Think about recent work. If a meter was changed or gas pipework altered, tell the engineer, as air in the pipe needs purging by a professional.
- Reset. The 200/400 Combi manual says to press the RESET button for 5 seconds. On a Combi 2 or Assure 500, follow the reset method in your user guide. Allow no more than 2 or 3 attempts in total, because each one makes another round of ignition attempts.
Our guide to a boiler that will not fire up covers the same checks for other makes.
If you smell gas, do not press reset. Turn the supply off at the meter if you can do so safely, open doors and windows, avoid light switches and naked flames, and call the National Gas Emergency Service on 0800 111 999. The same number is the one to call if gas is not reaching any of your appliances.
What the engineer will test
A Gas Safe registered engineer will measure the gas pressure at the boiler, inspect the electrode for wear and position, check the ignition cabling and confirm the gas valve opens and is set correctly. If those pass, they will look at the fan, the flue route, the earth circuit and the supply voltage, following the order in Baxi's troubleshooting section.
The exact sub-code also steers the diagnosis. E.04.10 means the boiler never confirmed a flame, which points first at gas, the gas valve and the spark. E.04.12 relates to flame monitoring, which the 200/400 Combi manual words as a false flame signal, so the electrode and its wiring come under closer scrutiny there. E.04.13 and E.04.17 send the engineer straight to the fan or the gas valve circuit. That is why the full code matters more than the E04 at the front.
Typical repair costs in the UK
| Job | Typical cost |
|---|---|
| Engineer call-out and diagnosis | Typically £60 to £150 |
| Ignition electrode replaced | Typically £90 to £180 |
| Ignition lead or spark generator | Typically £100 to £200 |
| Gas valve replacement | Typically £180 to £350 |
| Flue repair or adjustment | Typically £150 to £400 |
When you book, give the full code (E.04.10, not just E04), the model and whether other gas appliances work. Mention any recent meter change, gas work or power cut, and how many resets you have tried. If the boiler is under its Baxi warranty, contact Baxi first. Our Baxi fault code hub lists the other Baxi codes we cover.