BoilerFaultCodesWhat the manual says
Manufacturer manualFlow/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
Avoid the next call-out bill
A cover plan would handle faults like S.98: no call-out fees, no surprise bills.
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Related fault codes
All 148 fault codes on the ecoTEC Pro 28
Seeing a different code? Every code this model can display, in one place.