High Lockout
Boiler sensor on Ideal Concord CXC 48 116

Your boiler has detected that the temperature sensor used to monitor the water inside the unit is broken or sending incorrect signals.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Boiler sensor fault detected by diagnostic feature.

What causes this fault?

This fault occurs when the internal electronic sensors can no longer accurately measure the temperature of the water moving through the boiler. The most common reason is that the sensor's internal resistance has failed due to age or heat stress, but it can also be triggered by loose or corroded electrical connections between the sensor and the main control board.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
Search the official register →

Related guides you might find useful

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →