Error E2 351

Safety precautions:

- Before doing anything switch the boiler to stand-by and isolate electrical power at the boiler isolator or consumer unit. If you are unsure how to do this, do not proceed. Do not attempt to work on the gas or burner assembly.

- Work only when the boiler is cool. Wear eye protection and avoid touching electrical contacts unless power is isolated.

- If you smell gas or suspect a gas leak, leave the property immediately and call the gas emergency number. Do not attempt any checks.

Initial checks a homeowner can do (no cover removal beyond an access panel unless competent):

1. Note the exact fault shown (E2 351) and take a photo of the display. Record boiler model and serial number for the engineer.

2. Try a simple reset: restore power, then press and hold the reset button or follow the 3-second reset method for your model. Wait to see if the fault clears. One or two resets are acceptable; do not keep resetting repeatedly.

3. Check visible wiring and connectors: with the boiler powered off, look for any obvious loose or disconnected plug or cable from the lower front or service panel area. Some sensors have external plug connections that are safe to reseat if you can access them without removing the main cover. Do not force connectors.

4. Check system water pressure on the boiler gauge. Very low pressure can cause circulation problems and misleading sensor readings. Top up pressure only using the correct filling link method for your boiler if you know how.

Specific diagnostic and fix steps (suitable for competent DIYers only; otherwise call a professional):

1. Isolate power at the mains and remove the small front service panel if you are competent and comfortable doing so. Only proceed if you understand basic electrical safety.

2. Locate the central heating flow NTC sensor and its cable. The flow sensor is usually clipped into the flow pipe close to the heat exchanger and has a small 2- or 3-pin connector to the wiring loom.

3. Inspect the sensor lead and connector for loose pins, corrosion, water ingress or damaged insulation. If the connector has come free, reseat it firmly and ensure the locking tab engages.

4. If the connector is corroded or the cable is damaged, do not attempt to repair complicated wiring yourself unless qualified. A temporary dry wipe and careful reseat may help, but replacement should be done by an engineer.

5. Restore power and reset the boiler. If the E2 351 clears and the boiler operates normally, monitor for recurrence and arrange a service to check the sensor and connections properly.

6. If the fault remains after reseating or you find visible damage to the sensor/cable, isolate the boiler and contact a Gas Safe registered engineer. Provide them with the error code E2 351, any other cause codes shown in the info menu, and describe any checks you carried out. If possible, take photos of the sensor, connector and wiring to speed diagnosis.

When to call a professional:

- If you are not comfortable isolating power and opening the service panel, call a Gas Safe engineer.

- If reseating the connector does not fix the fault, or if the fault returns, you should have a qualified engineer replace the flow sensor, repair wiring, or check the control electronics/PCB.

- Any internal electrical, soldering, wiring replacement or gas-side work must be performed by a registered Gas Safe engineer.

Additional notes:

- Repeated resets without fixing the underlying cause can lead to further lockouts and may hide progressive sensor or PCB faults.

- Keep a record of the fault code, cause code, and any actions you took. That information plus photos will help the engineer diagnose and repair the issue more quickly.

- Avoid attempting to bypass or short sensors to force the boiler to run; this is unsafe and will likely invalidate warranty and service agreements.