Baxi Duo-tec Combi HE Fault codes & diagnostics

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

Combi Natural Gas 24-40 kW 2006-2008 Discontinued

Replaced by: Baxi Platinum Combi HE

The Duo-tec range comes in 4 types

Pick the one you have. The fault codes, GC numbers and manual differ by type.

Each model has its own manual A family spans several manuals, one per model or generation. Pick your model above and its page has the manual its fault codes were read from.

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.
10 High

All 10 documented codes

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E20

Your boiler's temperature sensor is failing, which prevents it from correctly monitoring how hot the water inside the system is getting.

High Engineer only £120-200 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Central Heating NTC Sensor
  • Wiring harness

Related codes

E28

Your boiler's flue sensor is failing to provide accurate temperature readings, so the system has shut down as a safety precaution to prevent overheating.

High Engineer only £150-250 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Flue NTC Sensor
  • Wiring Harness

Related codes

E50

Your boiler is unable to read the temperature of the water it is heating, so it has turned off the hot water supply to prevent overheating.

High Engineer only £120-200 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Domestic Hot Water (DHW) NTC Sensor

Related codes

E110

Your boiler has detected that it is overheating and has automatically switched itself off to prevent damage.

High Engineer only £150-300 Shared across the Duo-tec Combi range

Parts commonly replaced

  • NTC sensor
  • Central heating pump
  • Diverter valve
  • Primary heat exchanger

Related codes

E119

Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.

High DIY-safe £80-150 Shared across the Duo-tec Combi range

What to check first

  1. Locate the external filling loop, usually consisting of a small flexible hose with one or two valves underneath the boiler.
  2. Open the valve(s) slowly to let water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.
  3. Close the valve(s) tightly and check for any leaks.

Parts commonly replaced

  • Pressure Relief Valve
  • Pressure Sensor
  • Expansion Vessel

Related codes

E125

Your boiler is struggling to move water around the system because it is detecting a blockage or a failure in the internal pump.

High Engineer only £180-350 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Central heating pump
  • Diverter valve
  • Flow sensor

Related codes

E130

Your boiler has detected that the exhaust gases are becoming too hot, so it has safely shut itself down to prevent any damage.

High Engineer only £150-250 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Flue NTC sensor
  • Primary heat exchanger
  • Pump

Related codes

E133

Your boiler has failed to ignite the gas needed to heat your water and home, so it has safely shut itself down.

High DIY-safe £120-250 Shared across the Duo-tec Combi range

What to check first

  1. Check if your gas supply is working by testing another gas appliance like a hob
  2. Ensure your gas meter credit is topped up if you have a prepayment meter
  3. Press the 'Reset' button on the front of the boiler for at least 3 seconds

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

E160

Your boiler has stopped working because the fan responsible for clearing exhaust gases away from the unit is not spinning or responding correctly.

High Engineer only £180-350 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • PCB

Related codes

E193

Your boiler is struggling to get water moving around the system correctly before it attempts to light the burner.

High Engineer only £150-300 Shared across the Duo-tec Combi range

Parts commonly replaced

  • Circulation Pump
  • Flow Switch
  • Wiring Harness

Related codes