BoilerFaultCodesYour boiler is currently running a brief automatic check on its temperature sensors and should return to normal operation shortly.
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: Flow/return temperature sensor self-test. The self-test for the flow/return temperature sensor is activated.
What causes this fault?
This occurs when the boiler pauses to compare the readings from its internal heat sensors to ensure they are reporting temperatures accurately. It is a standard safety routine designed to prevent the system from overheating due to a faulty sensor. While it may briefly stop the boiler from firing, it is typically a sign that the software is doing its job correctly.
DIY fix possible
Wait for 5-10 minutes for the internal test to completeIf the code persists, try resetting the boilerCheck that your radiator valves are open to ensure water can circulate
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.