BoilerFaultCodesVaillant S.97 Fault Code
Also written as S97 — same fault.
The Vaillant S.97 fault code means: your boiler is performing a routine internal check on its water pressure sensor and should resume normal operation once finished.. It appears on 28 Vaillant models in our database.
Technical description: Water pressure sensor self-test. The self-test for the water pressure sensor is activated.
What causes the Vaillant S.97 fault?
This occurs when the boiler's internal computer performs a safety check to ensure it is receiving an accurate reading from the water pressure sensor. It happens automatically to verify that the system is not running dry, which protects the internal components from overheating. Most often, this is just a momentary pause in operation, but if it persists, it may indicate the sensor is sending inconsistent signals or the wiring has become loose.
DIY fix possible
Wait up to 15 minutes for the automated test to completeCheck if the water pressure is between 1.0 and 2.0 barReset the boiler if the code remains on the screen for a prolonged period
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A cover plan would handle faults like S.97: no call-out fees, no surprise bills.
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Vaillant models that show the S.97 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoFIT Pure 435
- ecoFIT Pure 825 Repair: £120-250
- ecoFIT Pure 830 Repair: £100-250
- ecoFIT Pure 835 Repair: £100-200
- ecoFIT sustain 615
- ecoFIT sustain 618
- ecoFIT sustain 630
- ecoTEC
- ecoTEC 65kW
- ecoTEC exclusive Repair: £0-180
- ecoTEC exclusive 627
- ecoTEC Plus 620
- ecoTEC Plus 625
- ecoTEC Plus 630
- ecoTEC Plus 635
- ecoTEC plus 637
- ecoTEC Plus 826
- ecoTEC Plus 832
- ecoTEC Plus 840
- ecoTEC Plus 938
- ecoTEC Pro Repair: £130-220
- ecoTEC Pro / ecoTEC Plus
- ecoTEC Pro 24 Repair: £130-220
- ecoTEC Pro 28 Repair: £130-220
- ecoTEC Pro 30 Repair: £120-200
- ecoTEC sustain
- Home Combi
- Home System Repair: £120-220
Source
Vaillant S.97 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant ecoFIT sustain 630 manual (PDF)
- Vaillant ecoTEC manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026