Keston Combi 2 Fault codes & diagnostics

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

Combi Natural Gas 28-35 kW 2013-2018 Discontinued
GC Number 47-930-09

Replaced by: Keston Combi 2C

Download the Keston Combi 2 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

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

Fault codes

All 2 documented codes

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Ignition Lockout

Your boiler is trying to start but cannot get a flame going, so it has safely shut itself down to prevent gas from building up.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ignition lead
Full explanation for Ignition Lockout
Too Many Restarts

Your boiler is repeatedly trying and failing to ignite, causing it to lock itself out as a safety precaution.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Condensate trap
Full explanation for Too Many Restarts
Status & diagnostic codes

5 operating states & engineer diagnostics

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

2H Diagnostic This code is not a fault; it is an informational message confirming your boiler is correctly configured for the standard natural gas supply used in the UK. 204 Diagnostic Your boiler is struggling to switch between heating your radiators and heating your hot water taps, which means you may have no hot water or heating until it is fixed. C13 Diagnostic Your boiler is struggling to breathe properly because the pipework that brings in fresh air and pushes out exhaust fumes is blocked, damaged, or incorrectly installed. C33 Diagnostic Your boiler is struggling to breathe properly because there is a problem with the pipework that brings in fresh air or pushes out exhaust fumes. C53 Diagnostic Your boiler has detected an issue with the airflow system that brings fresh air in and pushes waste gases out, preventing it from operating safely.