Remeha E.04.02 Fault Code: Causes, Fixes & Repair Costs
What does the Remeha E.04.02 fault code mean?
The E.04.02 code is part of Remeha's E04 ignition fault family, and the .02 sub-code tells you something specific: the igniter is producing a spark, but no stable flame is forming. The boiler has made repeated attempts to light the burner — typically more than five — without success, and has shut itself down as a precaution to prevent unburnt gas accumulating. This is distinct from E.04.01, where no spark is produced at all, and E.04.03, where a flame forms but the ionisation signal is too weak to be recognised. Because gas is being called for but not igniting, the boiler locks out until the root cause is addressed and the unit is reset. This is one of the more frequently seen fault codes on Remeha appliances and, while it can sometimes be cleared with a single reset, it nearly always requires a Gas Safe engineer to resolve properly.
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
- Gas supply interrupted or at incorrect pressure Common
If the gas supply to the boiler has been turned off, is at low pressure, or contains air — for example after supply work on the street or a prepayment meter running out — the burner will never catch regardless of how well the ignition system is working. This is the first thing to rule out before suspecting any component.
- Worn or contaminated ignition electrode Common
The ignition electrode generates the spark that lights the burner. Over time the tip erodes, becomes coated in carbon deposits, or the electrode bends out of its correct position relative to the burner. Any of these prevent the spark from reaching the gas at the right moment or with enough intensity, so the boiler sparks but nothing ignites.
- Gas valve not opening correctly Sometimes
The gas valve controls the flow of gas to the burner at the moment of ignition. If it sticks, fails electrically, or does not open fully, there is simply not enough gas present for the spark to ignite. This produces the classic E.04.02 symptom: a spark with no resulting flame.
- Incorrect gas-to-air combustion ratio Sometimes
If the mixture of gas and air reaching the burner is out of balance — typically identified by a CO₂ reading outside specification on a flue gas analyser — ignition can be unreliable or fail entirely. This sometimes develops gradually as components age or after servicing work that disturbed the gas valve settings.
- Faulty or degraded flue seals Sometimes
Leaking seals on the combustion chamber door, burner, or flue connection can allow combustion gases to recirculate back into the air intake. This dilutes the fresh air supply to the burner and makes reliable ignition very difficult, particularly during cold starts.
- PCB fault Rare
The printed circuit board controls the ignition sequence, gas valve, and flame detection circuitry. A failing PCB can send incorrect signals — for instance, opening the gas valve too briefly or mistiming the spark — producing an ignition fault even when the physical components are in good condition. PCB faults are less common but worth considering when other causes have been ruled out.
How to fix it
- Check that your gas supply is working DIY safe
Turn on a gas hob or check another gas appliance in your home. If nothing is working, the problem is with your gas supply rather than the boiler. Check your meter has credit if you are on a prepayment meter, and make sure the gas isolation valve on the pipe leading to the boiler is in the open (in-line) position. If your supply appears to be off, contact your gas network operator.
- Check and restore boiler pressure if needed DIY safe
Look at the pressure gauge on the boiler front panel. It should read between 1.0 and 1.5 bar when cold. If it is below 0.8 bar, top it up using the filling loop — consult your boiler manual for the location and procedure. Do not pressurise above 2.0 bar. Low pressure alone will not cause E.04.02, but it is worth correcting before resetting.
- Reset the boiler once or twice DIY safe
Press and hold the reset button (refer to your model's manual for its exact location) for around three seconds, then release and allow the boiler a full minute to attempt ignition. If it locks out again immediately, try once more. Do not reset more than two or three times in quick succession — repeated resets on a boiler that is failing to light push unburnt gas through the system and will not cure the underlying problem.
- Engineer to inspect the ignition electrode and lead Gas Safe engineer
A Gas Safe engineer will remove the boiler casing, visually inspect the ignition electrode for wear, carbon fouling, or physical distortion, and check the electrode gap against specification. The ignition lead connecting the electrode to the PCB will also be tested for continuity and replaced if damaged. These components are inside the combustion chamber and must not be touched by anyone other than a registered engineer.
- Engineer to test and clean or replace the flame sensing electrode Gas Safe engineer
On Remeha appliances the flame sensing electrode (ionisation probe) is separate from the ignition electrode. The engineer will test the ionisation signal with appropriate equipment, clean the probe if it is sooted up, and replace it if the signal remains out of specification. A faulty sensor can cause the boiler to behave as though no flame formed even when one did.
- Engineer to inspect the gas valve Gas Safe engineer
The engineer will check gas pressure at the valve inlet and outlet and test the valve's electrical solenoids. If the valve is not opening correctly or is delivering the wrong pressure to the burner, it will need to be adjusted, serviced, or replaced. Gas valve work is legally restricted to Gas Safe registered engineers.
- Engineer to check combustion ratio with a flue gas analyser Gas Safe engineer
Using a calibrated flue gas analyser, the engineer measures the CO₂ percentage in the flue gases and compares it against the Remeha specification for your model. If the ratio is off, they will adjust the gas valve modulation settings accordingly. This adjustment requires specialist equipment and gas-side access.
- Engineer to inspect flue seals and combustion chamber integrity Gas Safe engineer
The engineer will examine the seals on the combustion chamber door, burner gasket, and flue connections for signs of deterioration or leakage. Damaged seals allow flue gas recirculation which disrupts ignition. Any faulty seals will be replaced.
- Engineer to diagnose and replace the PCB if required Gas Safe engineer
If all the above checks are clear, the engineer will test the PCB's control outputs — particularly the signals to the gas valve and ignition transformer — to determine whether the board itself is at fault. PCB replacement on Remeha boilers typically takes one to two hours once the part is available; if the board needs ordering it may be three to five working days before the boiler is back in service.
- Call a Gas Safe registered engineer Gas Safe engineer
If the boiler has not cleared after your reset attempts, or if it keeps returning to E.04.02, you need a Gas Safe engineer to carry out a proper diagnosis. You can verify any engineer's registration at gassaferegister.co.uk before they begin work. Do not continue resetting a boiler that repeatedly locks out on this code.
Parts you may need
- Ignition electrode and lead assembly · from £55
- Flame sensing (ionisation) electrode · from £40
- Gas valve · from £180
- PCB (printed circuit board) · from £280
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 £150–£400, depending on the underlying cause.
Frequently asked questions
What is the difference between Remeha fault codes E.04.01, E.04.02, and E.04.03?
These three codes all belong to the E04 ignition fault family but indicate different stages of the ignition sequence failing. E.04.01 means the boiler is not producing a spark at all — typically pointing to a faulty ignition electrode, lead, or ignition transformer. E.04.02 (this code) means a spark is present but no flame forms — the gas is not igniting, which usually points to a gas supply issue, a faulty or dirty ignition electrode, or a gas valve problem. E.04.03 means a flame does form but the ionisation signal from the flame sensor is too weak for the boiler to recognise it as a stable flame, often caused by a worn or sooted ionisation probe. Knowing which sub-code you have helps an engineer go straight to the most likely cause.
Can I fix Remeha E.04.02 myself?
There is very little a homeowner can safely do beyond checking the gas supply is on, topping up the system pressure if needed, and resetting the boiler once or twice. Any work involving the ignition electrode, gas valve, flame sensor, flue, or PCB is legally restricted to Gas Safe registered engineers. Repeatedly resetting a boiler that keeps locking out on this code is not safe and will not solve the underlying fault.
How much does it typically cost to fix E.04.02 in the UK?
For most people, the repair falls between £150 and £400 including parts and labour. Replacing an ignition electrode and lead is usually £150 to £250 all-in. A gas valve replacement typically costs £250 to £400. A call-out and diagnostic visit alone is generally £60 to £120, which is often credited against the repair if you proceed. PCB replacement is the most expensive possibility at £400 to £650 including labour, but this is relatively uncommon and would only be recommended after other causes have been eliminated.
My Remeha boiler keeps showing E.04.02 after I reset it — what should I do?
A single successful reset after which the fault does not return can sometimes indicate a temporary gas supply blip. However, if the fault comes back within a few firing cycles, or recurs regularly, there is an underlying component fault that a reset cannot fix. Stop resetting and call a Gas Safe engineer. Continuing to reset a boiler that cannot light means repeatedly asking it to push gas through the combustion chamber without igniting it, which is unsafe.
Is my Remeha boiler worth repairing if it keeps getting E.04.02?
For most faults in the £150 to £400 range, repair makes sense if the boiler is under ten years old and has been regularly serviced. If the boiler is over twelve years old and the engineer identifies a PCB fault or a combination of worn components, the total repair cost may approach or exceed the cost of a new boiler — at which point replacement is worth considering. Ask your engineer for an honest assessment before committing to expensive parts on an ageing appliance.