Medium
d.88 on Vaillant ecoTEC sustain

Your boiler is struggling to detect the flow of water needed to start heating your hot water tap, likely due to a sensor issue or a drop in water pressure.

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

Flow rate limit value for ignition in domestic hot water mode

Shared across the ecoTEC sustain 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.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

d.87View →F.73View →

All 153 fault codes on the ecoTEC sustain

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

conConnectiond.00d.01d.02d.04d.05d.06d.07d.08d.09d.10d.11d.13d.14d.15d.16d.17d.18d.20d.21d.22d.23d.25d.27d.28d.33d.34d.35d.36d.39d.40d.41d.43d.45d.47d.50d.51d.58d.60d.61d.64d.65d.66d.67d.68d.69d.71d.73d.75d.77d.80d.81d.82d.83d.84d.85d.90d.91d.93d.94d.95d.96ErrF.00F.01F.1F.10F.11F.13F.20F.22F.23F.24F.27F.28F.29F.32F.46F.49F.61F.62F.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.77F.83F.84F.85F.87F.88F.89F.97F22F70P.00P.01P.02P.06S.00S.01S.02S.2S.03S.3S.04S.4S.05S.06S.6S.07S.08S.8S.10S.11S.13S.14S.15S.16S.17S.20S.21S.22S.23S.24S.25S.26S.27S.28S.30S.31S.32S.34S.39S.42S.53S.54S.88S.91S.96S.97S.98S.108S.109

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