High Lockout
PP4 on Grant Vortex

Your boiler has stopped working because one of its internal sensors is failing to monitor the temperature of the water returning to the unit.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Return gas sensor failure

What causes this fault?

This fault occurs when the boiler's control board loses communication with the sensor that measures the temperature of the water coming back from your radiators. The most common reason is that the sensor itself has developed an electrical fault or the wiring connecting it to the main controller has become loose or damaged.

Engineer required

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

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Related fault codes

PP1View →PP2View →PP3View →PP5View →

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