BoilerFaultCodesGrant PP4 Fault Code
The Grant PP4 fault code means: your boiler has stopped working because one of its internal sensors is failing to monitor the temperature of the water returning to the unit.. It appears on 2 Grant models in our database.
Technical description: Return gas sensor failure
What causes the Grant PP4 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 fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Grant models that show the PP4 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Grant PP4 fault code information on this page is sourced and cross-checked against the official Grant service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026