Baxi EP Fault codes & diagnostics

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

Natural Gas 1990-2005 Discontinued

Replaced by: EP2000

No manual available yet We don't hold the official service manual for this model yet. We're sourcing it — check back soon.

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
6 High 1 Medium 3 Low
Just want the most common Baxi EP faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 10 documented codes

Tap any card for details

1 red flash

Your boiler has sensed that it is getting too hot too quickly or that water isn't moving through the system properly.

High DIY-safe £120-280

What to check first

  1. Check that your radiator valves are open
  2. Ensure the system pressure is between 1 and 1.5 bar
  3. Reset the boiler by turning the selector switch to 'R' for five seconds

Parts commonly replaced

  • Temperature Sensor (NTC Thermistor)
  • Circulation Pump
  • Overheat Thermostat

Related codes

Full explanation for 1 red flash
2 red flashes

Your boiler has become too hot and has automatically shut itself down as a safety precaution.

High DIY-safe £100-£350

What to check first

  1. Ensure all radiator valves are fully open to allow water to circulate
  2. Check that your system pressure is between 1 and 1.5 bar on the gauge
  3. Allow the boiler to cool down, then move the selector switch to 'R' to reset

Parts commonly replaced

  • Circulating Pump
  • Overheat Thermostat
  • Thermistor (NTC Sensor)

Related codes

Full explanation for 2 red flashes
3 green flashes

Your boiler has temporarily lost its flame and is currently trying to restart itself automatically.

Medium DIY-safe £100-250

What to check first

  1. Wait for the boiler to complete its automatic self-reset sequence
  2. Check that other gas appliances in the home are working correctly
  3. Ensure the external condensate pipe has not frozen if the weather is cold
  4. Monitor the control panel to see if the fault clears or turns into a solid red light

Parts commonly replaced

  • Flame sensing electrode
  • Gas valve
  • Ignition lead

Related codes

Full explanation for 3 green flashes
3 red flashes

Your boiler has tried to light itself several times without success, so it has shut down as a safety precaution.

High DIY-safe £100-£250

What to check first

  1. Check that your gas supply is turned on at the meter
  2. If you have a prepaid meter, ensure you have sufficient credit
  3. Turn the selector switch to the reset position for five seconds, then back to the on position

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Flame Sensing Lead

Related codes

Full explanation for 3 red flashes
4 green flashes

Your boiler is having a temporary 'conversation' issue between its internal computer parts and will usually fix itself shortly.

Low DIY-safe £0-120

What to check first

  1. Wait for the boiler to self-reset as this is often a temporary glitch
  2. Turn the power to the boiler off and back on at the fused spur switch
  3. Monitor the lights to see if the flashing sequence changes or stops

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • External Controller

Related codes

Full explanation for 4 green flashes
5 green flashes

Your boiler's internal computer has encountered a temporary settings glitch and is currently trying to fix itself.

Low DIY-safe £0-350

What to check first

  1. Wait for the boiler to automatically reset itself
  2. Turn the power to the boiler off and back on at the fused spur switch
  3. If the flashing continues for more than 30 minutes, contact a Gas Safe engineer

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

Full explanation for 5 green flashes
5 red flashes

Your boiler's internal memory chip has developed a communication fault or become corrupted, preventing the system from starting up.

High Engineer only £120-300

Parts commonly replaced

  • Parameter Storage Unit (PSU)
  • Main Control Board (PCB)

Related codes

Full explanation for 5 red flashes
6 green flashes

Your boiler has experienced a small glitch and is trying to clear the problem on its own without you needing to do anything.

Low DIY-safe £0-120

What to check first

  1. Wait for the boiler to complete its self-reset cycle
  2. Monitor the lights to see if they return to a solid green status
  3. If the flashing persists for more than 30 minutes, try turning the power switch off and back on once

Parts commonly replaced

  • None (Software reset)
  • PCB (if fault becomes permanent)

Related codes

Full explanation for 6 green flashes
6 red flashes

Your boiler has encountered a general electrical or communication error and needs to be reset to try and clear the fault.

High DIY-safe £100-280

What to check first

  1. Locate the selector switch on the front of the boiler.
  2. Turn the switch to the 'Reset' position and hold it for five seconds.
  3. Return the switch to the original 'On' position and wait to see if the green light remains steady.

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • External wiring harness

Related codes

Full explanation for 6 red flashes
Status & diagnostic codes

1 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

1 green flash Status Your boiler has reached the required temperature and is naturally pausing its heating cycle; everything is working exactly as it should.