Vaillant Gas boiler fault P.02

What it means

After successful ignition, the product is operated at minimum heat input if the flow rate in the heating circuit permits this. Otherwise, the product does not ignite and remains in waiting mode with status code S.85.

Likely causes

1. Insufficient flow rate in heating circuit preventing minimum load operation
2. Burner wear or damage requiring replacement

Where to start

1. Run check programme and observe whether product ignites at minimum heat input
2. If product does not ignite, check status code display for S.85 (waiting mode)
3. Verify flow rate in heating circuit