Baxi boilers are pretty complicated pieces of kit, meaning there’s a long list of potential problems they can encounter if things stop working as they should.
If you notice that your Baxi boiler isn’t providing your home with hot water or that your central heating isn’t functioning correctly, you’ll likely see an error code displayed on the system’s interface. These codes help engineers determine the problem quickly, especially if the issue isn’t obvious from other signs right away.
To make the process easier, this guide covers common Baxi boiler fault & error codes by model, plus the most frequent codes, what they usually mean, and what you can safely check.
Baxi Platinum+ 40kW error codes
If performance and reliability are at the top of your list of priorities when looking for a new or replacement boiler, the Baxi Platinum+ will struggle to disappoint. Thanks to its high power rating, this boiler is an ideal option for larger homes with around 20 radiators and families with greater hot water demands.
Baxi’s Platinum+ is a firm favourite among boiler engineers too, as its front access panel means any repairs or adjustments can be carried out easily.
- Error code: E20
Problem: Central heating negative temperature coefficient (NTC) fault. - Error code: E28
Problem: A fault with either the flue NTC, air pressure switch, or wiring or a blocked flue or condensate pipe. - Error code: E50
Problem: Hot water NTC fault. - Error code: E110
Problem: The safety thermostat was triggered due to internal overheating. The pump may need unblocking or replacing. Contact a Gas Safe engineer. - Error code: E119
Problem: Low water pressure. - Error code: E125
Problem: Circulation fault (primary circuit). - Error code: E130
Problem: Flue NTC tripped. An internal fault with the flue or the external flue pipe could be blocked. - Error code: E133
Problem: Interruption of the gas supply or flame failure. - Error code: E160
Problem: Fan or fan wiring fault. - Error code: E193
Problem: Pre-circulation fault.
Baxi 600 Combi / Baxi 800 Combi error codes
Two similar models with matching error codes, the Baxi 600 and 800 are both great heating solutions. The Baxi 600 is all about performance and delivery in small spaces, making it a great choice for smaller homes.
The Baxi 800 is a slight step up from that, boasting increased capacity and performance, making it a more suitable option for larger homes with greater hot water requirements.
- Error code: E09
Problem: An issue with the gas valve connection cable. - Error code: E15
Problem: Gas valve command fault. - Error code: E20
Problem: Central heating NTC fault. - Error code: E28
Problem: Flue NTC fault. - Error code: E40
Problem: Central heating return NTC fault. - Error code: E83
Problem: No communication. - Error code: E109
Problem: Pre-circulation fault. - Error code: E110
Problem: One of the following issues may be present:- The boiler’s max temperature exceeded for gradient (probable pump jammed or air in the circuit)
- The boiler’s max temperature exceeded (probable pump jammed or air in the circuit)
- The safety thermostat sensor has been triggered.
- Error code: E118
Problem: The primary system water pressure is too low (< 0.5 bar). - Error code: E125
Problem: Circulation fault (primary). - Error code: E128
Problem: Frequent flame failure (12 times). - Error code: E129
Problem: Safety error for frequent loss of flame with max correction during the ignition during Calibration Function. - Error code: E130
Problem: Flue thermostat sensor tripped (lockout). - Error code: E133
Problem: Failure to light (could be a gas supply issue). - Error code: E134
Problem: Elapsed time gas valve open without gas (short request in a short period). - Error code: E135
Problem: Interruption of gas supply (internal error). - Error code: E154
Problem: Flow/return sensor temperature test. - Error code: E160
Problem: Fan or wiring fault. - Error code: E270
Problem: Circulation fault. - Error code: E321
Problem: Hot water NTC fault. - Error code: E384
Problem: False flame.
Baxi 600 Heat error codes (flashing lights)
The Baxi 600 Heat is a standard boiler that can fit in a typical kitchen cupboard. There are various outputs available for this model, from 13kW to 30kW.
This is a boiler that embodies the phrase “small but mighty”, making it a good choice for homeowners looking for a powerful boiler that doesn’t take up too much space.
The error codes display differently on the Baxi 600 Heat boiler, as shown below:
Green flashes
- Error code: 2 flashes green
Problem: The BL terminals on the User Interaction and Controller are open circuit. - Error code: 3 flashes green
Problem: No flame was detected during operation. - Error code: 4 flashes green
Problem: Bad connection, a wiring fault or an internal communication fault. - Error code: 5 flashes green
Problem: Parameter error or a faulty PU. Configuration error or a PCB fault. - Error code: 6 flashes green
Problem: Possible internal fault in the combustion control unit.
Red flashes
- Error code: 1 flash red
Problem: Bad connection to flow or the return temperature sensor. - Error code: 2 flashes red
Problem: One of the following issues may be present:- Over-temperature thermostat on the heat exchanger activated
- No water flowing through the heat exchanger
- PCB over-temperature condition
- Flue fault resulting in recirculation or activation of the air pressure switch (if fitted).
- Error code: 3 flashes red
Problem: No ignition, no flame detected following ignition or a false flame signal detected. - Error code: 4 flashes red
Problem: Fan calibration error or fan failure. - Error code: 5 flashes red
Problem: Bad connection to PU, parameter error or a faulty PU. - Error code: 6 flashes red
Problem: Bad connection, wiring fault or parameter error.
Baxi 200 Combi / Baxi 400 Combi error codes
In a similar dynamic to the ones we’ve mentioned before, the Baxi 200 and 400 are sibling boilers with slightly different qualities.
The Baxi 200 Combi is a compact unit with an output as high as 24kW in the newest edition. The 400 is more suited to larger homes, with a maximum output of 30kW.
The error codes are the same on these boilers to save confusion.
- Error code: H.01 – .00
Problem: Temporary loss of communication between gas valve and boiler board. Fault in the air/gas unit. - Error code: H.01 – .05
Problem: The maximum difference between the flow and return temperature exceeded. Non-existent or insufficient circulation. Sensor error. - Error code: H.01 – .08
Problem: The flow temperature is increasing too fast in heating mode. Non-existent or insufficient circulation. - Error code: H.01 – .14
Problem: Maximum flow temperature value exceeded. Non-existent or insufficient circulation. - Error code: H.01 – .18
Problem: No circulation of water. Non-existent or insufficient circulation. Sensor error. - Error code: H.01 – .21
Problem: The flow temperature is increasing too fast in DHW mode. Non-existent or insufficient circulation. Sensor error. - Error code: H.02 – .02
Problem: No input of parameters C1/C2. PCB not configured. - Error code: H.02 – .03
Problem: Incorrect configuration settings C1/C2. - Error code: H.02 – .04
Problem: Parameter error. Incorrect parameters. - Error code: H.02 – .06
Problem: System water pressure. Water leak in the boiler. Water leak in the system. - Error code: H.03 – .00
Problem: Communication error with NTC flue sensor. Sensor not, or badly connected. Bad connection. Sensor fault. - Error code: H.03 – .01
Problem: Communication error with the HMI PCB. HMI is not connected. - Error code: H.03 – .02
Problem: No flame during operation. No ionisation current. - Error code: E.00 – .04
Problem: Return temperature sensor open-circuit. Sensor not or badly connected. Bad connection. Sensor fault. - Error code: E.00 – .05
Problem: Return temperature sensor open-circuit. Sensor not or badly connected. Bad connection. Sensor fault. - Error code: E.01 – .04
Problem: Loss of flame has been detected 5 times in 24 hours (with the burner on). No ionisation current. - Error code: E.01 – .11
Problem: Incorrect fan speed. External draught over the boiler. Defective gas/air unit. - Error code: E.01 – .12
Problem: Reset required. The temperature measured by the return sensor is greater than the flow temperature. - Error code: E.01 – .17
Problem: No circulation. Sensor not or badly connected. Sensor fault. - Error code: E.01 – .20
Problem: Maximum flue gas temperature value reached (>140ºC). No circulation. Sensor fault. - Error code: E.02 – .00
Problem: A boiler reset is in progress after the reset button was pressed. - Error code: E.02 – .07
Problem: No or low system water pressure. Low system pressure (less than 0.5 bar) boiler will not function. - Error code: E.02 – .16
Problem: On board CSU time-out. Check PCB for damage. - Error code: E.02 – .17
Problem: Permanent loss of communication between gas valve and boiler PCB. Fault in air/gas unit. Loose connection to the gas valve. - Error code: E.02 – .19
Problem: Jumper 1 changed. Check the position of jumper 1. - Error code: E.02 – .20
Problem: Jumper 2 changed. Check the position of jumper 2. - Error code: E.02 – .21
Problem: Jumper 3 changed. Check the position of jumper 3. - Error code: E.02 – .47
Problem: Connection to external device unsuccessful. Check wiring to the external device. - Error code: E.02 – .48
Problem: Configuration to external device unsuccessful. Check pairing to external. - Error code: E.04 – .00
Problem: Gas valve fault. Gas valve not detected. - Error code: E.04 – .01
Problem: Flow temperature sensor short-circuited. Sensor not or badly connected. Bad connection or a sensor fault. - Error code: E.04 – .02
Problem: Flow temperature sensor open-circuited. Sensor not or badly connected. Bad connection or sensor fault. - Error code: E.04 – .03
Problem: Critical flow temperature reached. Non-existent or insufficient circulation. - Error code: E.04 – .04
Problem: The flue temperature sensor has short-circuited. Sensor not or badly connected. Bad connection or a sensor fault. - Error code: E.04 – .05
Problem: The flue temperature sensor is open-circuited. Sensor not or badly connected or a sensor fault. - Error code: E.04 – .06
Problem: Critical flue gas temperature value reached. No circulation. Sensor fault. - Error code: E.04 – .08
Problem: Maximum safe temperature value reached. No circulation. Sensor not or badly connected. Bad connection or sensor fault. - Error code: E.04 – .10
Problem: Failure to light (could be a gas supply issue). - Error code: E.04 – .12
Problem: False flame signal. - Error code: E.04 – .13
Problem: The fan rotor is blocked. Fan seized or wiring to fan damaged. - Error code: E.04 – .17
Problem: Problem with gas valve. Possible defective gas/air unit.
Baxi Duo-Tec / Baxi Megaflo error codes
The Baxi Duo-Tec is able to fit in a space as small as 290mm deep and can connect with the Baxi uSense smart thermostat system to help keep your home’s energy usage (and bills) to a minimum.
The Megaflo is a cylinder-based system made with larger homes and high hot water demands in mind. If you’ve got multiple bathrooms and need hot water from several different outlets simultaneously, the Megaflo could be the perfect solution for you.
- Error code: E09
Problem: An issue with the gas valve connection cable. - Error code: E15
Problem: Gas valve command fault. - Error code: E20
Problem: Central heating NTC fault. - Error code: E28
Problem: Flue NTC fault. - Error code: E40
Problem: Central heating return NTC fault. - Error code: E83
Problem: No communication. - Error code: E109
Problem: Pre-circulation fault. - Error code: E110
Problem: Safety thermostat operated. - Error code: E118
Problem: The primary system water pressure is too low (< 0.5 bar). - Error code: E125
Problem: Circulation fault (primary). - Error code: E128
Problem: Frequent flame failure (12 times). - Error code: E130
Problem: Flue thermostat sensor tripped (lockout). - Error code: E133
Problem: Failure to light (could be a gas supply issue). - Error code: E135
Problem: Interruption of gas supply (internal error). - Error code: E154
Problem: Flow/return sensor temperature test. - Error code: E160
Problem: Fan or wiring fault. - Error code: E270
Problem: Circulation fault. - Error code: E321
Problem: Hot water NTC fault. - Error code: E384
Problem: False flame.
Most Common Baxi Boiler Fault Codes
E119 (Low Water Pressure)
What it means: Your system pressure has dropped too low to operate safely.
Causes:
- Recent radiator bleeding
- Small system leak
- Expansion vessel or pressure relief valve issue
Fix:
- Check pressure gauge (should read 1.0-1.5 bar)
- Use the filling loop to top up system
- Reset the boiler
- If pressure drops regularly, a leak or faulty part is likely – book a pressure check.
E133 (Ignition Failure)
What it means: The boiler is failing to ignite or the flame has been lost.
Causes:
- Frozen condensate pipe
- Faulty flame sensor or gas valve
- Air in the gas line
DIY Check:
- Make sure your gas supply is on
- Check for frozen outdoor pipes in winter
- Press the reset button
- Recurring E133 errors may require sensor replacement or gas valve servicing.
E160 (Fan Fault)
What it means: The boiler’s fan isn’t running or isn’t being detected.
Causes:
- Broken fan motor
- Wiring or PCB fault
- Flue blockages
What to do:
This one needs a Gas Safe engineer. A non-functioning fan can prevent safe venting of gases.
E168 (Unknown Fault)
What it means: The boiler has encountered a general error it can’t categorise.
Causes:
- Power interruptions
- Internal software fault
- Multiple minor issues
Fix:
- Power off boiler for 30 seconds
- Turn back on and press reset
- If E168 persists, it often means an underlying issue like a faulty PCB or sensor.
How to Reset a Baxi Boiler
To reset most Baxi boilers:
- Locate the reset knob or button (usually marked with a circular arrow)
- Press and hold for 3-5 seconds
- Wait for boiler to reboot
Important: Never reset a boiler more than once without checking the cause. Continuous resets may damage internal components.
