Emergency
Group 1, 5 flashes on Worcester Bosch Greenstar CDi Compact

Your boiler has detected a potential internal gas leak or a sensor fault that prevents it from starting safely to protect your home.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

What the manual says

Manufacturer manual

Ionisation detected after burner stopped; Gas valve leaking; False flame detected; Gas valve EV2 leak test failed; Gas valve EV1 leak test failed; Ionisation current detected before burner-start; Gas valve error; Ionisation sensor shorted

From this model's manual
Verified against the Greenstar 27 30 RiCompact ErP installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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