High
Err on Vaillant ecoTEC sustain

Your boiler's internal control computer has lost its electrical connection, meaning it cannot process commands or operate normally.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

Fault: Interface communication Interface PCB not connected or connected incorrectly, short circuit in the cable harness

From this model's manual
Verified against the Vaillant/Vaillant Ecotec Sustain installation & service manual, page 52.
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 is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F.70View →F.71View →

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.88d.90d.91d.93d.94d.95d.96F.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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