Medium
B02 on Ariston Microsystem 15

Your boiler is struggling to communicate with your wall thermostat, meaning it doesn't know when to turn your heating on or off.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Room Thermostat

Shared across the range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check if your thermostat batteries need replacingEnsure your thermostat is switched on and showing a displayTurn the boiler off and back on at the fused spur to reset the connection

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Related fault codes

B03View →

All 93 fault codes on the Microsystem 15

Seeing a different code? Every code this model can display, in one place.

1 011 031 041 051 061 071 091 101 121 141 161 181 P11 P21 P31 P42 053 013 023 033 043 053 063 073 P94 114 124 135 015 025 045 P15 P25 P36 106 127 017 027 037 117 127 137 227 237 5010121314108591A01A02A03A04A05A06A07A08A09A10A11A12A33AA0011AA0022AA0033AA0077AA3333AA9999B01B03B05B06B07B08BOILER SHUTDOWNE08E33E95EE 0044EE 0055EE 0088EE 2200EE 9999Ignition LockoutINSUFFICIENT WATERInsufficient water pressureL.E.D. DL.E.D. GLimescale Build-upSafety Shut-off

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