Baxi E55 Fault Code: Causes, Fixes & Repair Costs
What does the Baxi E55 fault code mean?
The E55 code on a Baxi boiler indicates that the boiler's internal electronics have detected a communication failure. In plain terms, the boiler's printed circuit board (PCB) has lost reliable contact with one or more of its connected components — such as the gas valve, pump, or a sensor — and has shut the boiler down as a precaution. In some cases E55 is also triggered when the gas valve requires re-calibration, meaning the valve is present and connected but is not responding within the parameters the PCB expects. Either way, the boiler cannot safely fire until the underlying electronics issue is resolved.
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
- PCB fault or internal PCB damage Common
The PCB is the boiler's central control unit, coordinating every component from the fan and pump through to the gas valve. If the board itself develops a fault — whether through component failure, a cracked solder joint, or corrosion — communication breaks down and E55 is triggered. PCB damage from moisture or condensation is a particularly common culprit, since even small amounts of water vapour settling on the board can cause electrical shorts or corrosion on the circuit tracks.
- Loose, corroded, or damaged internal wiring Common
The PCB communicates with components via a network of wiring harnesses and plug connectors. Over time — especially in older boilers or those that have experienced vibration or heat cycling — connectors can work loose, terminals can corrode, or wire insulation can deteriorate. A single intermittent connection is enough to trigger an E55 communication fault.
- Gas valve calibration failure Sometimes
Baxi boilers require the gas valve to operate within precise parameters. If the valve drifts out of calibration — due to normal wear, a pressure fluctuation, or a previous repair — the PCB may detect that the valve is not responding as expected and log an E55 fault. This does not necessarily mean the valve has failed; it may simply need re-calibrating by an engineer using dedicated software or test equipment.
- Failed or failing connected component Sometimes
Components such as the pump, fan, or a pressure sensor that fail to communicate correctly with the PCB can also produce an E55. The PCB sends a command and receives no response, or an out-of-range signal, causing it to lock out. The fault in this scenario lies with the component rather than the board itself, but the symptom presented to the user is the same communication error code.
How to fix it
- Attempt a single boiler reset DIY safe
Locate the reset button on your Baxi boiler's front panel — on most models it is marked with a flame or reset symbol. Press and hold it for roughly 1–3 seconds until the boiler restarts and the display clears. Allow the boiler a full ignition cycle to see whether it fires normally. One reset attempt is reasonable; if E55 returns immediately or within a short time, do not keep pressing reset. Repeated resets will not fix an electronics fault and can mask information an engineer needs.
- Check that your gas supply is working DIY safe
Before calling an engineer, confirm that other gas appliances in your home (hob, gas fire) are working normally. If they are not, the issue may be with your gas supply rather than the boiler. In that case, contact your gas supplier or, if you smell gas, call the National Gas Emergency Service on 0800 111 999 immediately.
- Inspect wiring connections and re-seat any loose plugs — engineer task Gas Safe engineer
A Gas Safe engineer will open the boiler casing and systematically check every wiring harness and plug connector on the PCB and at each connected component. Loose or corroded connectors are re-seated or replaced. This is often the quickest and least expensive resolution when wiring is the root cause.
- Carry out gas valve calibration — engineer task Gas Safe engineer
If wiring checks out, the engineer will test the gas valve's response and, where required, perform a calibration procedure. On Baxi boilers this typically involves using manufacturer diagnostic software or a combustion analyser alongside the valve's adjustment points. Gas valve work must only be performed by a Gas Safe registered engineer — it is illegal and dangerous to attempt it otherwise.
- Diagnose the PCB using test equipment — engineer task Gas Safe engineer
The engineer will use a multimeter to check voltage levels and continuity at key points across the PCB — testing that signals are correctly reaching the fan, pump, gas valve, and sensors. Readings that fall outside normal ranges indicate a faulty section of the board. In some cases a cracked solder joint can be repaired on-site; more commonly, a board that has burned, corroded, or suffered component failure will need replacing entirely.
- Replace the PCB or faulty component as required — engineer task Gas Safe engineer
Once the root cause is confirmed, the engineer will fit a replacement PCB or whichever component has failed. Baxi PCBs are model-specific, so the correct part must be sourced before the visit where possible. After fitting, the engineer will run a full commissioning check to confirm normal operation and clear the fault.
- Call a Gas Safe registered engineer if E55 persists after one reset DIY safe
If the fault returns after a single reset attempt, stop and arrange a visit from a Gas Safe registered engineer. You can verify any engineer's registration at gassaferegister.co.uk. Electronics and communication faults on a Baxi boiler are not user-serviceable beyond the initial reset.
Parts you may need
- Baxi PCB (model-specific) · from £220
- Gas valve (Baxi compatible) · from £130
- Wiring harness / connector set · from £35
- Pump (if identified as failing component) · from £75
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–£450, depending on the underlying cause.
Frequently asked questions
Can I fix a Baxi E55 fault myself?
The only action a homeowner should take is a single reset attempt. Beyond that, E55 points to an internal electronics or communication fault — wiring inspection, PCB diagnosis, and any gas valve work all require a Gas Safe registered engineer. Removing the boiler casing and working on internal electrical or gas components yourself is unsafe and, for gas-related work, illegal without Gas Safe registration.
How much does it cost to fix a Baxi E55 in the UK?
Most E55 repairs fall in the range of £150–£450 including parts and labour. A wiring fix or gas valve re-calibration is typically at the lower end. A PCB repair (for example, re-soldering a cracked joint) usually costs £150–£250 all in. A full PCB replacement is the most expensive common outcome, typically £300–£500 for parts and labour combined, though costs can exceed this on older or less common Baxi models where parts are harder to source. Engineers in London and the South East generally charge 10–20% more than those in the North or Wales. Most engineers also charge a diagnostic fee of £60–£100 to confirm the root cause before quoting for the repair itself.
Will my boiler warranty cover an E55 fault?
It may do, depending on the age of your boiler and whether it has been serviced annually by a Gas Safe engineer — most Baxi warranties require this. Check your warranty documentation or contact Baxi directly with your boiler's serial number. If the boiler is out of warranty, some heating cover plans (such as those offered by British Gas, HomeServe, or your energy supplier) may cover PCB or gas valve repairs after an excess payment.
Why does my Baxi keep showing E55 after I reset it?
If E55 returns repeatedly after resetting, the underlying fault — most likely a PCB issue, a loose wiring connection, or a gas valve calibration problem — has not gone away. The boiler is locking out each time it detects the same communication error. Continuing to reset without investigation is unlikely to resolve anything and may delay a repair that is easier and cheaper to fix early. Arrange a visit from a Gas Safe engineer to diagnose the root cause properly.