Error E2 222

Safety first

- If the boiler is showing E2 222, turn the boiler off at the main front panel and isolate the electrical supply at the boiler isolator or mains switch before opening the casing. Do not attempt gas-side repairs unless you are a Gas Safe registered engineer. If you smell gas, evacuate and call the gas emergency number immediately.

Initial homeowner checks (safe, non-intrusive)

1. Try a simple reset: press and hold the reset button for the time shown in your manual (typically 3 seconds). Wait and see if the code clears and the boiler re-starts. If the code returns immediately or within a short time, proceed to further checks.

2. Note recent events: has the boiler been serviced recently, has there been water ingress, condensation, or work near the boiler that could have disturbed wiring? Any corrosion or water on the boiler electronics? Record the error code and take photos of the display and connectors if accessible.

3. Check boiler water pressure and system conditions: while not a direct cause of a shorted sensor, low pressure or air in the system can create other sensor-related faults; top up pressure only if you know how and it is safe to do so.

Visual inspection (with power isolated)

1. Isolate electrical supply to the boiler and confirm it's dead. Remove the outer casing following the manufacturer's instructions.

2. Locate the flow temperature sensor: typically screwed into the flow header or pipework close to the heat exchanger and connected by a small two- or three-wire connector to the control box. Inspect the sensor body, wiring, and plug for signs of damage, pin corrosion, water ingress, chafing, melted insulation or foreign conductive debris bridging the pins.

3. Disconnect the sensor plug and inspect the connector pins for bridging or corrosion. Sometimes pushing the connector back into place or cleaning/inspecting reveals a loose or wet connection that caused a short.

Electrical checks with a multimeter (only if you are competent and the power is isolated)

1. With the sensor unplugged and the boiler power isolated, use a multimeter on the resistance (ohms) scale to measure across the sensor wires (the two wires that go to the sensor). You are testing for a short circuit between sensor wires or a short to earth. If you measure a very low resistance (near 0 ohms) between the sensor wires, that indicates a short. If you measure infinite/very high resistance, that indicates an open circuit. If you are unsure what the correct resistance should be at ambient temperature, compare readings with a replacement sensor specification or call a professional. Avoid guessing values; the key diagnostic is whether the circuit is shorted or open.

2. Check for continuity from each sensor wire to boiler earth or to adjacent wiring: a short to earth will show continuity where there should be none.

3. Inspect the wiring harness between the sensor and the control board for damage. Gently move wiring while checking continuity to locate intermittent shorts from chafed insulation.

Basic fixes you can try (safe, non-gas work)

1. If you find a visibly corroded connector, clean and dry the pins with a dry brush or electrical contact cleaner and re-seat the connector. Ensure the connector is fully pushed home and locked.

2. If wiring insulation is damaged close to the connector and you are competent with low-voltage wiring, you may be able to replace a short section of wiring with suitable heat-resistant cable and proper crimps; otherwise, do not attempt and call an engineer.

3. After reassembly and restoring power, try a reset and observe whether the E2 222 clears.

When to call a professional (and why)

- If the fault persists after the simple reset and visual checks, or if you find a short in the wiring that you cannot safely repair, call a Gas Safe registered engineer. They will have the correct replacement sensor parts, wiring, tools and the authority to work on and test gas appliances.

- If the sensor tests OK but the code remains, the control board or the sensor input circuitry may be faulty; this requires a qualified engineer to diagnose and replace the correct component.

What to tell the engineer and what to prepare

- Tell them the exact boiler model (Worcester Bosch GB162), the fault code E2 222, and the results of any checks you did (reset tried, connector condition, multimeter readings if taken). Provide photos of the sensor, connector and wiring if possible. This speeds diagnosis and ensures they arrive with the correct parts.

Final notes

- Do not continue to operate the boiler while the fault persists. Avoid attempting gas-side repairs. Replacement of sensors or wiring faults is a common fix but should be completed by a Gas Safe engineer if you are not fully confident in electrical and boiler work. Keep the boiler service history up to date to help prevent recurring faults.