| 5 01 | Flame absence (ionisation not detected during ignition). | The gas valve may not open/modulate (coil fatigued, shaft/shutter seized), preventing gas from reaching the burner and thus ionisation. Check coil power supply during ignition attempt and measure pressures at valve/gauge ports; if it does not open with correct voltage, the valve is faulty. |
| 5 02 | Flame detected with gas valve closed. | If the gas valve remains partially open or loses tightness when the electronics close it, combustion persists and the electrode detects a flame "with the valve closed." Check that there is no voltage in the coil and, even so, there is pressure/gauge in the manifold; perform a tightness and closure test of the valve. |
| 5 P1 | First ignition attempt failed. | A gas block/valve that does not open on the first attempt (coil or mechanism seized) prevents gas from reaching and causes an immediate ignition fault. Check the ignition sequence: presence of voltage at the valve during 5P1 and absence of flow/pressure at the outlet; if there is correct control and it does not open, replace the valve. |
| 5 P2 | Second ignition attempt failed. | If the gas valve fails intermittently or continues not to open after the first attempt, the second attempt also does not provide sufficient gas and 5P2 is recorded. Confirm control voltage and measure pressure at the valve outlet during the attempt; if there is no flow with control present, the valve is the cause. |
