BoilerFaultCodesYour boiler is temporarily paused because it has detected a potential issue with its internal sensors while performing a self-test.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Automatictestprogramme:Returntemperaturesensor,heatingdemandsblocked.
What causes this fault?
This fault occurs when the boiler performs a safety check and notices that the temperature sensors for the water going out and coming back are giving conflicting or illogical readings. The most common reason is that one of the sensors has developed a fault or is starting to wear out, preventing the boiler from accurately monitoring its own performance. It pauses the heating process to ensure it doesn't overheat or run inefficiently based on incorrect data.
DIY fix possible
Wait for 15-30 minutes to see if the status clears automatically after the self-test finishesSwitch the boiler off at the fused spur switch, wait 30 seconds, and switch it back onPress the 'Reset' button (indicated by a flame with a line through it) for five seconds
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like S.98 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.