Baxi E55 fault codewhat it means and how to fix it
"Calibration Required": the gas valve has not been set up to the board after a PCB or valve change. An engineer's combustion-analyser job, not a fault a householder can clear.
Take care
Get a Gas Safe registered engineer to look at your Baxi E55
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What E55 means
E55 appears in one Baxi document in this family, the 2012 Duo-tec 2 Combi GA user guide, as "Calibration Required", and its meaning is exactly that. These boilers run a gas valve whose relationship to the fan speed is learned by the board rather than set with a screwdriver, and when a new PCB is fitted, a new gas valve is fitted, or the board loses its stored values, it needs an engineer to run the calibration routine with a combustion analyser on the flue sampling point before it will run normally. Until that is done the board shows E55 and will not fire, or fires only in a restricted mode, because it has no trusted setting for the gas-to-air ratio.
Baxi do not print E55 in the 600 and 800 tables or on the professional page — on those boilers the calibration state is entered from the panel and the manuals describe it as a procedure rather than a fault — so this page is scoped to the Duo-tec 2 Combi GA, where the user guide lists it, and to the Compact ranges of the same period, which share its control.
There is no householder action. The user guide shows E55 with the spanner symbol, which "cannot be reset by the user", and a reset would be pointless because the board is not reporting a fault so much as an unfinished job. An E55 on a boiler that has just had work done means the engineer left without calibrating; an E55 on a boiler nobody has touched means the board has lost its settings, which is a board problem.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| New PCB or gas valve not calibrated | The most common case. A board or valve has been replaced and the calibration routine, which requires a combustion analyser, has not been run or was not completed. | Common |
| Board lost its stored settings | A brownout or an internal fault has cleared the learned gas-valve values. The board returns to the uncalibrated state and asks for the routine again. | Occasional |
| PCB fault | A board that repeatedly forgets its calibration is a board that is failing. Recalibrating it is a temporary fix. | Rare |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£80–£150
Time on site
45 minutes
A calibration visit £80–£150 if the last engineer has to return. Part of the labour on a PCB or gas valve replacement.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Baxi / Potterton / Main gas valve
7683968£120–£240Authorised Baxi parts distributor
Price checked 28 September 2026
Baxi / Potterton / Main main PCB
£150–£320Authorised Baxi parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Baxi fault codes
- E168Get it checkedTrade lists call E168 a Baxi PCB lockout, but no Baxi UK manual or error-code page prints it. Treat it as a board fault: one power cycle, then an engineer.Related: electronics and power
- E83Usually simple to fixE83 to E87: the boiler has lost contact with a connected control — a room unit or programmer wired to the board. Check the control first; the boiler itself is usually fine.Related: electronics and power
- E103Get it checkedSafety Assist codes E103, E104 and E107: the battery-backed safety board on the 600 and 800 is exhausted, faulty or out of step with the main board. Contact your installer; there is no reset.Related: electronics and power
- E.02.47Usually simple to fix"Connection to external device unsuccessful": a Baxi 200/400 Combi or Combi 2 has lost a control it was paired with. Check the control and its wiring; Baxi's remedy is the auto-detect function.Related: electronics and power
- E317Get it checkedMains frequency out of range (shown on some boards as 162). The boiler, not the supply, is almost always the odd one out. Check other appliances, then call an engineer.Related: electronics and power
- E385Get it checkedUnder-voltage (shown on some boards as 165): the supply at the board dropped below what it will run on. Usually a house-wiring or supply problem the boiler is reporting, not causing.Related: electronics and power
Own a Baxi boiler? Save it and its codes come first next time.
Related guides
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.