BoilerFaultCodesTechnical description
Outside temp. sensor or lambda probe faulty.
What causes this fault?
This fault occurs when the boiler's internal computer receives conflicting or missing data from its environmental sensors. It most commonly happens because the lambda sensor, which monitors the exhaust gases, has failed or the wiring connecting the external temperature sensor has become damaged or loose.
This fault is more frequently reported during the first cold snap of autumn, as the boiler attempts to communicate with the outside temperature sensor after months of inactivity.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register →