Baxi 200 Combi (range) Fault codes & diagnostics

42 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 24-28 kW 2018-present

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
40 High 1 Medium 1 Low
Just want the most common Baxi 200 Combi (range) faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 42 documented codes

Tap any card for details

E.00 – .04

Your boiler has detected a problem with the internal sensor that monitors water returning from your radiators, meaning it cannot safely regulate its temperature and has stopped working.

High Engineer only £90-160

Parts commonly replaced

  • Return temperature sensor (NTC thermistor)
  • Sensor wiring harness
  • PCB
Full explanation for E.00 – .04
E.00 – .05

Your boiler has detected a fault with the sensor that monitors water temperature returning to the unit, meaning it cannot operate safely or efficiently.

High Engineer only £90-160

Parts commonly replaced

  • Return Temperature Sensor (NTC Thermistor)
  • Wiring Harness
  • Main Control Board
Full explanation for E.00 – .05
E.01 – .02

Your boiler has detected that the water coming back from your radiators is hotter than the water leaving the boiler, which usually means water is flowing in the wrong direction or a sensor has developed a fault.

High Engineer only £120-£280

Parts commonly replaced

  • Flow/Return NTC thermistor
  • Water pump
  • Main PCB
Full explanation for E.01 – .02
E.01 – .04

Your boiler is struggling to keep its flame lit and has safely shut down after repeatedly failing to stay on.

High DIY-safe £100-350

What to check first

  1. Check that your gas emergency control valve is open and any pre-paid gas meter has credit.
  2. Verify if other gas appliances, like a hob, are working to rule out a wider gas supply issue.
  3. Restart the boiler by turning the selector switch to the 'Reset' position for five seconds.

Parts commonly replaced

  • Ignition electrode
  • Flame sensing probe
  • Gas valve
  • Condensate trap
Full explanation for E.01 – .04
E.01 – .11

Your boiler's fan is not spinning at the correct speed, which is preventing the system from safely clearing exhaust fumes.

High Engineer only £250-£450

Parts commonly replaced

  • Fan assembly
  • Gas valve
  • Air pressure switch
  • Main PCB
Full explanation for E.01 – .11
E.01 – .12

Your boiler has stopped working because it believes the water returning to the unit is hotter than the water leaving it, which usually indicates a circulation problem or a sensor error.

High DIY-safe £90-180

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar on the gauge
  3. Press and hold the 'R' or Reset button for five seconds

Parts commonly replaced

  • NTC Return Sensor
  • NTC Flow Sensor
  • Internal Pump
Full explanation for E.01 – .12
E.01 – .17

Your boiler has stopped working because water isn't moving through the system correctly or a internal sensor has lost its connection.

High DIY-safe £120-280

What to check first

  1. Locate the reset button or selector switch on the front of the boiler panel
  2. Press and hold the reset button for at least five seconds
  3. Check that your radiator valves are open and that the system pressure is between 1 and 1.5 bar

Parts commonly replaced

  • Circulation Pump
  • Temperature Sensor (NTC)
  • Wiring Harness
Full explanation for E.01 – .17
E.01 – .20

Your boiler has switched itself off because it has become too hot inside, likely due to water not flowing correctly or a faulty internal sensor.

High DIY-safe £120-350

What to check first

  1. Check that your home's radiator valves are fully open
  2. Ensure your system pressure is between 1 and 1.5 bar on the pressure gauge
  3. Try resetting the boiler by turning the selector switch to 'R' for five seconds

Parts commonly replaced

  • Flue Overheat Thermostat
  • Main Heat Exchanger
  • Circulation Pump
Full explanation for E.01 – .20
E.02 – .00

Your boiler is simply letting you know that the reset button has been held down or activated.

Low DIY-safe

What to check first

  1. Wait a few seconds for the boiler to complete its reboot cycle
  2. Check if the display returns to the standard temperature reading
  3. If the boiler was reset to clear a different fault, monitor to see if that original code returns
Full explanation for E.02 – .00
E.02 – .07

Your boiler has detected that there is not enough water in the central heating system to operate safely.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (the flexible silver hose) underneath your boiler.
  2. Slowly open the one or two taps on the loop until you hear water flowing.
  3. Watch the pressure gauge until it reaches 1.5 bar, then close the taps tightly.

Parts commonly replaced

  • Filling loop
  • Pressure sensor
  • Automatic air vent
Full explanation for E.02 – .07
Showing 11–20 of 42
E.02 – .16

Your boiler has experienced an internal electronic failure or a communication error between its main control components.

High Engineer only £250-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Internal Wiring Harness
Full explanation for E.02 – .16
E.02 – .17

Your boiler's computer has lost touch with the internal components that control the gas flow, meaning it cannot safely light the burner.

High Engineer only £180-350

Parts commonly replaced

  • Gas Valve
  • Printed Circuit Board (PCB)
  • Wiring Harness
Full explanation for E.02 – .17
E.02 – .19

Your boiler's internal computer settings have been altered or are mismatched, which is preventing the system from operating correctly.

High Engineer only £90-160

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Configuration Jumper
Full explanation for E.02 – .19
E.02 – .20

Your boiler's internal computer settings have been altered or misconfigured, preventing it from operating correctly.

High Engineer only £90-180

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • System Jumper/Link
Full explanation for E.02 – .20
E.02 – .21

Your boiler's electronic settings have been altered or are misconfigured, preventing it from operating correctly.

High Engineer only £80-160

Parts commonly replaced

  • Main PCB
  • Jumper Selector
Full explanation for E.02 – .21
E.02 – .47

Your boiler has detected a communication problem with your external thermostat or smart controls, meaning it cannot receive the command to turn on.

High DIY-safe £80-180

What to check first

  1. Check if your wireless thermostat has run out of batteries and replace them.
  2. Ensure the thermostat receiver (usually near the boiler) is switched on and showing lights.
  3. Try resetting the boiler by turning the selector knob to 'R' for five seconds.
  4. Check if your internet router is on if you use smart controls like Hive or Nest.

Parts commonly replaced

  • Batteries
  • External Thermostat
  • Control Wiring
  • Receiver Box
Full explanation for E.02 – .47
E.02 – .48

Your boiler is having trouble talking to your wireless thermostat or smart controller, meaning it doesn't know when to turn the heating on.

Medium DIY-safe £0-120

What to check first

  1. Check the batteries in your thermostat or wall controller and replace them if necessary
  2. Move your wireless thermostat closer to the boiler to see if it reconnects
  3. Press and hold the pairing button on the receiver box near the boiler to re-establish the connection

Parts commonly replaced

  • Wireless Receiver Box
  • External Smart Controller
  • Batteries
Full explanation for E.02 – .48
E.04 – .00

Your boiler has lost communication with the internal gas control system, meaning it cannot safely release fuel to create a flame.

High Engineer only £180-£350

Parts commonly replaced

  • Gas Valve
  • Wiring Harness
  • Printed Circuit Board (PCB)
Full explanation for E.04 – .00
E.04 – .01

Your boiler has stopped working because it cannot correctly measure the temperature of the water leaving the unit due to a faulty internal sensor or wiring.

High Engineer only £90-160

Parts commonly replaced

  • Flow Temperature Sensor (NTC Thermistor)
  • Wiring Harness
Full explanation for E.04 – .01
E.04 – .02

Your boiler has stopped working because it can no longer accurately measure the temperature of the water leaving the unit.

High Engineer only £90-160

Parts commonly replaced

  • Flow Temperature Sensor (NTC Thermistor)
  • Wiring Harness
Full explanation for E.04 – .02
Showing 21–30 of 42
E.04 – .03

Your boiler has shut down because water is not moving through the system properly, causing it to overheat.

High DIY-safe £120-£350

What to check first

  1. Check if your radiator valves are open
  2. Ensure the boiler pressure gauge is between 1 and 1.5 bar
  3. Check for frozen condensate pipes during cold weather
  4. Try resetting the boiler using the selector switch

Parts commonly replaced

  • Circulating pump
  • Primary heat exchanger
  • Flow temperature sensor
Full explanation for E.04 – .03
E.04 – .04

Your boiler has detected an issue with the sensor that monitors exhaust gases, and it has locked the system down as a safety precaution.

High Engineer only £90-180

Parts commonly replaced

  • Flue Temperature Sensor (NTC)
  • Wiring Harness
  • Main PCB
Full explanation for E.04 – .04
E.04 – .05

Your boiler has detected a problem with a safety sensor that monitors the temperature of the exhaust gases, causing the system to lock out.

High Engineer only £90-180

Parts commonly replaced

  • Flue temperature sensor (NTC)
  • Wiring harness
  • Main PCB
Full explanation for E.04 – .05
E.04 – .06

Your boiler has shut down because it is getting too hot inside, likely due to a lack of water flow or a faulty sensor safety check.

High DIY-safe £120-£350

What to check first

  1. Check if your central heating valves are open
  2. Ensure your radiator valves (TRVs) are turned up
  3. Check the boiler pressure gauge and top up to 1.5 bar if low
  4. Reset the boiler by turning the selector switch to 'R' for five seconds

Parts commonly replaced

  • Flue Thermistor (NTC Sensor)
  • Circulation Pump
  • Main Heat Exchanger (if scaled)
Full explanation for E.04 – .06
E.04 – .08

Your boiler has shut down because it has detected it is getting too hot, likely due to a lack of water flow or a sensor failure.

High DIY-safe £90-250

What to check first

  1. Check that the boiler pressure is between 1.0 and 1.5 bar on the gauge
  2. Ensure all radiator valves are fully open to allow water circulation
  3. Perform a reset by turning the selector knob to the 'R' position for five seconds

Parts commonly replaced

  • Pump
  • Overheat Thermostat
  • NTC Temperature Sensor
Full explanation for E.04 – .08
E.04 – .10

Your boiler is trying to start up but cannot light the gas flame to provide heating or hot water.

High DIY-safe £100-280

What to check first

  1. Check if other gas appliances, like a hob, are working to confirm gas supply.
  2. Verify that your gas meter has credit if you use a pre-payment meter.
  3. Reset the boiler by turning the selector switch to the 'R' position for five seconds.

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB (Printed Circuit Board)
Full explanation for E.04 – .10
E.04 – .12

Your boiler has detected a flame signal when there shouldn't be one, or it is running too hot to operate safely.

High Engineer only £120-350

Parts commonly replaced

  • Ionisation electrode
  • Gas valve
  • PCB (Main control board)
Full explanation for E.04 – .12
E.04 – .13

Your boiler's fan, which safely pushes exhaust fumes away, has stopped spinning or cannot communicate with the system.

High Engineer only £250-£450

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • Main PCB
Full explanation for E.04 – .13
E.04 – .17

Your boiler has detected a serious problem with its internal gas system and has shut down as a safety precaution.

High Engineer only £250-£450

Parts commonly replaced

  • Gas Valve
  • Printed Circuit Board (PCB)
  • Gas/Air Unit
Full explanation for E.04 – .17
H.01 – .00

Your boiler has lost its internal connection to the main gas control unit, meaning it cannot safely manage the fuel it needs to fire up.

High Engineer only £180-350

Parts commonly replaced

  • Gas Valve
  • Wiring Harness
  • Main PCB
Full explanation for H.01 – .00
Showing 31–40 of 42
H.01 – .05

Your boiler has detected that the water is heating up too quickly or isn't circulating properly through the system.

High DIY-safe £120-280

What to check first

  1. Check that the boiler pressure is between 1 and 1.5 bar on the gauge
  2. Ensure all radiator valves are fully open
  3. Check for any visible leaks around the boiler or pipework
  4. Restart the boiler using the reset button

Parts commonly replaced

  • Circulation Pump
  • Flow/Return Temperature Sensor (NTC)
  • Central Heating Filter
Full explanation for H.01 – .05
H.01 – .08

Your boiler is overheating because water isn't moving through the system quickly enough to be cooled down.

High DIY-safe £120-350

What to check first

  1. Check that your boiler pressure is between 1 and 1.5 bar on the gauge
  2. Ensure all radiator valves are fully open
  3. Restart the boiler using the reset button

Parts commonly replaced

  • Circulation pump
  • Flow temperature sensor (NTC)
  • Main heat exchanger (de-scaling)
Full explanation for H.01 – .08
H.01 – .14

Your boiler has detected that it is getting too hot too quickly, usually because water isn't moving through the system properly.

High DIY-safe £100-£350

What to check first

  1. Check that your boiler pressure is between 1 and 1.5 bar on the gauge.
  2. Ensure all radiator valves are fully open to allow water to flow.
  3. Restart the boiler to see if the temporary fault clears.

Parts commonly replaced

  • Circulation pump
  • Flow temperature sensor
  • Main heat exchanger (flushing)
Full explanation for H.01 – .14
H.01 – .18

Your boiler has stopped working because water is not moving through the system properly or a temperature sensor has detected an overheating issue.

High DIY-safe £120-£350

What to check first

  1. Check that your boiler pressure is between 1.0 and 1.5 bar on the internal gauge.
  2. Ensure all radiator valves and any isolation valves under the boiler are fully open.
  3. Attempt to reset the boiler by turning the selector switch to the reset position for five seconds.
  4. Bleed your radiators to remove any trapped air that may be blocking circulation.

Parts commonly replaced

  • Central heating pump
  • Temperature sensors (NTC thermistors)
  • Main heat exchanger (flushing/cleaning)
Full explanation for H.01 – .18
H.01 – .21

Your boiler is heating up too quickly when you turn the tap on, which usually means water isn't flowing through the system fast enough to take the heat away.

High Engineer only £120-£350

Parts commonly replaced

  • DHW Temperature Sensor (NTC)
  • Plate Heat Exchanger
  • Circulation Pump
Full explanation for H.01 – .21
H.02 – .02

Your boiler's internal computer brain hasn't been set up with the correct identity settings, so it doesn't know how to operate correctly.

High Engineer only £100-£350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Configuration Plug
Full explanation for H.02 – .02
H.02 – .03

Your boiler is temporarily confused by its internal software settings and cannot start up correctly.

High DIY-safe £80-160

What to check first

  1. Locate the selector switch or reset button on the front of the boiler.
  2. Turn the switch to the 'R' (Reset) position and hold for at least 5 seconds.
  3. Wait for the boiler to restart; if the code repeats, a Gas Safe engineer must reconfigure the internal board.

Parts commonly replaced

  • Printed Circuit Board (PCB)
Full explanation for H.02 – .03
H.02 – .04

Your boiler's computer brain is momentarily confused by some internal settings and cannot operate correctly.

High DIY-safe £90-280

What to check first

  1. Locate the selector knob on the front of the boiler control panel.
  2. Turn the knob to the 'Reset' position and hold it for five seconds.
  3. Return the knob to your desired setting and wait for the boiler to restart.

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Parameter chip
Full explanation for H.02 – .04
H.02 – .06

Your boiler has detected that the water pressure is too low for it to operate safely, likely due to a small leak or air in the system.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (braided silver hose) underneath your boiler.
  2. Slowly open the valve(s) until you hear water entering the system.
  3. Watch the pressure gauge and close the valves once it reaches between 1.0 and 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Pressure sensor
  • Automatic air vent
Full explanation for H.02 – .06
H.03 -.00

Your boiler has stopped working because its internal sensors or control system are struggling to talk to each other correctly.

High Engineer only £90-180

Parts commonly replaced

  • Central heating NTC temperature sensor
  • Flue sensor
  • Wiring harness
Full explanation for H.03 -.00
Showing 41–42 of 42
H.03 – .01

Your boiler's computer parts are having trouble talking to each other, which means the system cannot operate for heating or hot water.

High Engineer only £250-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring Harness
Full explanation for H.03 – .01
H.03 – .02

Your boiler has lost its flame while it was running, which means it has stopped providing heating and hot water for safety reasons.

High DIY-safe £120-350

What to check first

  1. Check if other gas appliances in your home, like a hob, are working to confirm gas supply.
  2. Ensure your gas meter has credit if you use a prepay meter.
  3. Press and hold the Reset button for five seconds to see if the boiler restarts.

Parts commonly replaced

  • Flame sensing electrode
  • Gas valve
  • Ignition lead
  • PCB
Full explanation for H.03 – .02