BoilerFaultCodesThe 6 most common faults
01
E01 High Engineer
Your boiler is failing to light the burner, meaning it cannot provide you with any heating or hot water until the ignition system is professionally serviced.
Full guide for E0102
E01 074 High Engineer
Your boiler is failing to light the flame properly because it cannot communicate with the internal safety controls.
Full guide for E01 07403
E01 075 High Engineer
Your boiler is failing to light the flame because there is a loose or damaged connection in the internal wire that creates the ignition spark.
Full guide for E01 07504
E01-074 High Engineer
Your boiler is failing to light the gas burner correctly to provide heating and hot water.
Full guide for E01-07405
E03-886 High Engineer
Your boiler has failed to ignite or stay lit correctly, meaning it will not be able to provide heating or hot water until it is reset or repaired.
Full guide for E03-88606
E03-893 High Engineer
Your boiler has detected an incorrect internal air-to-gas ratio, which prevents it from firing up safely.
Full guide for E03-893on the Keston K170
Ignition leadIgnition electrodePrinted Circuit Board (PCB)Ignition Control UnitPrinted Circuit BoardWiring harness
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Keston shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue