High Lockout
S.61 on Vaillant ecoTEC Pro 28

Your boiler has detected that its internal safety settings don't match the type of gas being supplied to the property, causing it to stop running for safety.

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

Fault: Incorrect gas type. The coding resistor on the PCB does not match the entered gas group (see also F.92).

What causes this fault?

This fault occurs when the boiler's internal computer detects a conflict between its hardware settings and the electronic signal from the gas valve. It is most commonly caused by incorrect programming during a part replacement or a technical failure in the main circuit board's ability to identify which type of gas it should be burning. Because the boiler cannot be sure it is burning fuel safely, it shuts down instantly as a protective measure.

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 fault codes

F.92View →S.58View →

Related guides you might find useful

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Pilot light keeps going out

Older boilers — thermocouple, draught, gas supply.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →