Your boiler is performing a routine self-check of the internal pump before it starts the main heating process.

Pump pre run

What causes this fault?

This status occurs as part of the boiler's normal start-up sequence to ensure the internal pump is moving water correctly before the burner ignites. It is not a breakdown, but rather a safety and efficiency check to prevent the heat exchanger from overheating. If this code stays on the screen for a long time, it may suggest that the pump is struggling to reach its required speed or there is air trapped in the system.