Baxi fault codes, explained properly
Baxi boilers show an E code with three digits. Here is what each of the common ones means, what causes it, and which ones you should stop resetting.
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Reviews from homeowners across the North East.
Reading a Baxi E code
Baxi uses E followed by three digits. Duo tec, Platinum and the 600 and 800 series all share the same code set, so the same number means the same thing whichever of those you have.
One Baxi code is worth flagging up front. E168 is deliberately generic and covers several underlying faults, so it is not diagnostic on its own. Anyone quoting a repair off an E168 without connecting to the appliance and reading its stored fault history is guessing.
The reset rule, and why it matters
Almost every fault code can be cleared with the reset button, and almost everyone presses it more than once. That is the single most expensive habit in domestic heating.
A lockout is the boiler protecting itself. Resetting it tells the appliance to try again. Once is reasonable, because genuine one off glitches do happen. Repeatedly resetting a boiler that is locking out on ignition means it is pumping gas into the combustion chamber and failing to light it, over and over. Repeatedly resetting an overheat lockout means asking it to fire again into a system that cannot carry the heat away. Both do real damage, and both turn a known price repair into a bigger one.
Reset once. If it locks out again, stop and get it looked at.
Baxi codes in detail
E133, ignition failure
The boiler has tried to light and failed, then locked out. It is the Baxi code we see most.
Why it happens: A frozen condensate pipe in cold weather, gas supply off or restricted, a worn ignition electrode, a gas valve fault, or low gas pressure at the appliance.
What you can do: Check other gas appliances work. Thaw an external condensate pipe with warm water. Reset once and no more.
What an engineer does: Tests working gas pressure, checks the electrode and lead, and verifies the gas valve before replacing anything. The board fault history usually shows whether this has been building for weeks.
E119, low water pressure
System pressure has dropped below the minimum the boiler will run at.
Why it happens: A leak, recently bled radiators, a pressure relief valve discharging outside, or a failed expansion vessel.
What you can do: Repressurise to 1.0 to 1.5 bar with the filling loop and watch how quickly it falls.
What an engineer does: Checks the external discharge pipe, tests the expansion vessel and pressure tests the system. The rate of loss narrows it down fast.
E125, circulation fault
The boiler cannot detect water moving through it properly.
Why it happens: A failed or airlocked pump, sludge blocking flow, or a motorised valve stuck closed. On older systems the valve is a common and often overlooked cause.
What you can do: Check pressure and whether any radiators heat. Beyond that it needs testing.
What an engineer does: Measures flow and return temperatures, checks the pump and any motorised valves, and assesses the system water. A cleaning job and a pump replacement are different answers and it is worth knowing which you need.
E128, flame lost during operation
The boiler lit and then lost the flame while running.
Why it happens: Gas pressure dropping under load, a flue restriction, a failing flame sensing electrode, or a condensate issue building up.
What you can do: Reset once. If it repeats, leave it, because a boiler losing flame repeatedly is a combustion problem.
What an engineer does: Flue gas analysis at full rate plus a working gas pressure test, which between them separate supply problems from appliance problems.
E160, fan fault
The fan is not running at the speed the board expects.
Why it happens: A worn fan, a wiring or connector fault, or a board not reading the signal. A corroded or restricted flue terminal makes a fan work harder and fail sooner, which is worth knowing on coastal and exposed properties.
What you can do: Nothing. The fan is inside a sealed chamber.
What an engineer does: Checks the fan speed signal and current draw and inspects the flue for restriction, rather than fitting a fan and finding the terminal was the cause.
E168, general system alert
A generic code that can cover several underlying faults. It tells you something is wrong without saying what.
Why it happens: Deliberately broad. It needs the fault history reading off the board to be meaningful.
What you can do: Note anything you have observed, such as when it happens and whether heating or hot water is affected. That genuinely helps.
What an engineer does: Connects to the appliance, reads the stored fault history, and works from that rather than from the code on the display.
E110, overheat
The boiler has exceeded its safe temperature and shut down.
Why it happens: Poor circulation, almost always. Pump failure, sludge, a closed valve, or a thermistor reading wrongly.
What you can do: Do not sit resetting it. Each reset fires the boiler into a system that cannot take the heat away.
What an engineer does: Checks circulation first, then the system water condition, then the sensors. If the system is heavily sludged the honest answer is a clean rather than a part.
What these repairs cost
One fixed diagnosis fee to attend and find the fault, then one fixed price for the repair itself, agreed before anything is ordered. No hourly billing and no figure that moves once the case is off.
Sensors and thermistors are the cheapest parts, fans and pumps sit in the middle, and boards and gas valves are the expensive end. The published list is on our boiler repair cost page.
E125 and E110 both very often come back to system water rather than a boiler part. If yours is full of magnetite, a proper system clean is the repair, and fitting a pump into a dirty system simply brings the fault back. Baxi warranties run up to 10 years when registered, and the annual service is the condition that keeps them valid.
Baxi questions we get asked
The common ones before we attend.
What does E168 actually mean on a Baxi? +
E133 clears when I reset but comes back the next cold morning. +
Is E110 dangerous? +
Which Baxi models do you work on? +
Is it worth repairing an older Baxi? +
Where do you cover? +
Other brands and what to do next
- Worcester Bosch fault codes
- Vaillant fault codes
- Ideal boiler fault codes
- Navien fault codes
- Look any code up in the error code checker
- What a boiler repair actually costs
- Boiler repair across the North East
- Out of hours emergency cover
- Annual boiler servicing
Local pages: Sunderland, Durham, Washington, Chester le Street and Houghton le Spring.
There is a longer write up of one specific code here: the Baxi E133 error code explained.